(The Doctor and Jo are being ferried to a small island in an even smaller boat.)
ROBBINS: That's it over there.
(The Doctor looks through a pair of binoculars at what is really Norris Castle on the Isle of Wight.)
DOCTOR: There you are, Jo. That's the Master's permanent residence from now on.
JO: Well, let's hope he's still there.

[Quay]

(They moor up and walk along the jetty.)
DOCTOR: Okay.
ROBBINS: I'll be back in a couple of hours to take you over to the mainland.
DOCTOR: Right.
(Robbins wheels a small motorbike while the Doctor and Jo get into a stripped out Citroen 2CV with no doors.)

[Governor's office]

(In the castle, an older man picks up the internal telephone.)
TRENCHARD: Yes?
BARCLAY [OC]: Main gate. Two visitors for the prisoner, sir, from UNIT. Passes all in order, sir.
TRENCHARD: Right, send them up.
(The Doctor and Jo are let in through the gate and showed up to the office by an armed guard. Trenchard is working at his desk.)
DOCTOR: Well, I suppose we could always come back later.
TRENCHARD: Oh, yes, of course. You'll be the chappie from UNIT.
JO: My name's Josephine Grant. How do you do? And this is the Doctor.
TRENCHARD: Colonel Trenchard. Delighted to meet you. Pleasant trip?
DOCTOR: Yes, thank you.
TRENCHARD: You're late, you know.
JO: Yes, we were held up.
TRENCHARD: Mmm, thought you might have sunk without trace.
JO: Sunk?
TRENCHARD: Happens all the time recently.
DOCTOR: What does?
(Trenchard gives a piece of paper to the guard, who leaves with it.)
TRENCHARD: Ships vanishing. Makes you think, doesn't it?
DOCTOR: It does indeed.
TRENCHARD: Now then, passes?
DOCTOR: Well, look, we've been through all that...
TRENCHARD: We don't take any chances here. Let's see them.
(Jo hands them over.)
TRENCHARD: Oh. Thank you. Ah yes, from UNIT.
DOCTOR: That's right, yes.
TRENCHARD: Yes. Ah, jolly good. Well, you'll be wanting to see the prisoner.
DOCTOR: That was the general idea.
TRENCHARD: He's an interesting chap, you know. You'll enjoy talking to him.
DOCTOR: If ever I get the opportunity. Has he given you any trouble as yet?
TRENCHARD: Not a bit.
JO: You've got to be joking! He must have tried to escape?
TRENCHARD: You've seen our security precautions. Anyway, we're on an island.

[The Master's cell]

(Trenchard leads the way along a corridor to the cell and enters. The Master is working out on a rowing machine.)
TRENCHARD: Visitors for you.
MASTER: Why, Doctor! And Miss Grant! What a very pleasant surprise.
DOCTOR: Yes, well, how are you?
MASTER: Well, as you see, very well. Trying to keep fit.
TRENCHARD: Yes, well, I'll leave you all together. Give the guard a shout when you want to leave.
DOCTOR: Thank you, Colonel.
(Trenchard leaves.)
MASTER: He's quite a decent sort, really. Used to be the Governor of a colony once, so he tells me.
DOCTOR: Very small colony, wasn't it? In fact, I believe they claimed independence soon after he arrived.
JO: He seems to be looking after you very well.
MASTER: Oh, yes, I've got everything I want, except, of course, my freedom.
DOCTOR: You can consider yourself lucky. Quite a few people were in favour of having you executed.
MASTER: My dear Doctor, don't think I'm not grateful. I've had a chance to think about things while I've been in here.
DOCTOR: Have you now?
MASTER: I wish that something like this had happened a long time ago.
JO: Surely you don't like being locked up?
MASTER: No, but... it's given me a chance to reconsider my life.
DOCTOR: Am I to take it that you're a changed man?
(The Master washes his hands in the en-suite.)
MASTER: Is that so very incredible? After all, I do have a great deal of which to repent.
JO: You're telling us.
DOCTOR: In that case, perhaps you'd like to tell me the whereabouts of your Tardis?
MASTER: So that you could use it in order to escape from this planet, Doctor?
DOCTOR: No, so that I can make absolutely certain that you can't.
MASTER: No, I'm sorry. That is too much to ask.
DOCTOR: Ask a silly question. Come on, Jo. I think we'd better be going. Is there anything that I can do for you at all?
MASTER: There is one thing. Please come in now and then to have a chat. Oh, Trenchard's a very nice man, but his conversation is somewhat limited.
JO: Goodbye.
MASTER: Goodbye, Miss Grant. And goodbye, Doctor. I sincerely hope we meet again very soon.
(The Doctor nearly shakes the Master's hand, but turns the gesture into a wave.)
DOCTOR: Goodbye.
(The Master gets back on his rowing machine, laughing.)

[Governor's office]

JO: Doctor?
DOCTOR: Mmm?
JO: You felt sorry for him, didn't you. You wanted to come down here and see that was all right.
DOCTOR: Well, he used to be a friend of mine once. A very good friend. In fact, you might almost say we were at school together.
JO: How long's he going to be here?
DOCTOR: Forever, I should think.
(Trenchard enters.)
TRENCHARD: Ah, ready for off, then? I'd better stamp your passes.
DOCTOR: What, again?
TRENCHARD: Got to be checked in and out, old man. It's the rule. Well, we don't look after him too badly, do we?
DOCTOR: No, indeed. But I advise you to be careful. He's a very dangerous man, you know.
TRENCHARD: Ah, don't worry. I keep my eye on him. There you are, my dear. Come along now then.
JO: Thank you.
TRENCHARD: I'll get one of my chaps to run you down to the quayside.
DOCTOR: Thank you.

[The Master's cell]

(Trenchard enters. The Master is doing a crossword. Times, probably.)
TRENCHARD: There we are, then. Fooled them nicely, didn't we?
MASTER: Don't underestimate the Doctor. Do you really believe that he came here to see me?
(The Master takes a dictionary from a bookcase to help with his crossword.)
TRENCHARD: Why else?
MASTER: Vanishing ships, of course.
TRENCHARD: Oh, I don't think so. No, he didn't seem particularly interested when I mentioned it.
MASTER: You did what!
TRENCHARD: We were just chatting. No harm done, surely.

[Quay]

ROBBINS: Ah, it's true. Three ships vanished. Something queer going on for all their trying to hush it up.
DOCTOR: Well, who's trying to hush it up?
ROBBINS: Well, them over at the naval base. The secret research establishment.
DOCTOR: You seem to know a great deal about all this.
ROBBINS: Well, I'm in the lifeboat crew, aren't I? We went out to look for survivors. Only found the one lifeboat, capsized. The bottom was all charred in a sort of pattern.
DOCTOR: Well, where's this boat now?
ROBBINS: Ah, the Navy took it. Told us to keep our mouths shut.
DOCTOR: Well, where's this naval base, then?
ROBBINS: Over beyond the headland.
DOCTOR: Right, well, perhaps you'd like to take me there straight away.
ROBBINS: Mister Trenchard paid me to bring you out here and take you back. You want to go over to the naval base, then you make your own arrangements.
DOCTOR: Yes, well, you're probably perfectly right. Look, er, I wonder whether you'd like to go and see what's happening to my young friend? She said she was going to buy some picture postcards.
(The Doctor holds up a note of the realm.)
ROBBINS: I don't mind.
DOCTOR: I'd go myself, only... my bad leg's playing me up a bit. The Crimea, you know.
ROBBINS: Crimea?
DOCTOR: Oh, Gallipoli? El Alamein? Does it really matter?
ROBBINS: I reckon not.
(Robbins takes the money and leaves. The Doctor unties the little boat, starts up the engine and chugs away.)

[Hart's office]

(At HMS Seaspite Naval Research Establishment, Captain Hart is giving dictation to his secretary, a young WREN.)
HART: The charred ship's lifeboat will be sent to our laboratory at HMS Vernon Portsmouth for investigation and analysis. Meanwhile, we are keeping careful watch...
BLYTHE: Yes, sir?
HART: Come and look at this. What on Earth?
(The Doctor is steering the boat up onto the beach.)
BLYTHE: Perhaps he's lost, sir.
HART: This place is supposed to be top secret. People treating it like Brighton beach.
(Hart picks up a telephone.)
HART: Get me the Master at Arms. Captain Hart here. I don't know whether you've noticed but there happens to be a stray civilian chugging into the base!

[Naval base beach]

(The Doctor crunches his way over the shingle to an upturned boat and gets out his magnifying glass to examine the burn marks.)
M-A-A: Oi! You!
(The Master at Arms leads five armed ratings at the double.)
DOCTOR: Good afternoon. I wonder whether I could see your commanding officer.

[Quay]

(Jo gives Robbins a ten pound note.)
ROBBINS: Thank you, Miss.
(Robbins gives Jo his motorcycle helmet.)
ROBBINS: Look after it for me, won't you?
JO: Don't worry. I'll bring it back just as soon as I've found the Doctor.
(Jo rides off on his motorcycle.)

[Outside Hart's office]

HART: If you are from UNIT, then where are your credentials?
DOCTOR: I never carry the things. A lot of bureaucratic nonsense. If you wish to see my pass, then ask Miss Grant.

[Hart's office]

HART: Why didn't you arrange for an official visit through normal channels?
DOCTOR: Well, I just dropped in purely on impulse, old chap. As soon as I heard about that charred lifeboat, I had to see it.
HART: Oh? Why?
DOCTOR: You've inspected the boat yourself?
HART: Well, of course I have.
DOCTOR: Then you must have noticed the linear nature of those scorch marks. Excuse me, my dear. May I?
(The Doctor takes Blythe's shorthand pad and pencil.)
DOCTOR: Thank you. Now then, sit down. Now, the marks are a very definite shape, a linear shape like this. Now, how do you account for that?
(The Doctor draws a series of wavy lines on the pad.)
HART: A freak affect if the ship caught fire.
DOCTOR: Yes, but it didn't catch fire. If it had, the smoke and flames would have been seen, wouldn't they?
HART: All right then, how do you account for them?
DOCTOR: A concentrated beam of heat, applied from underneath the boat whilst it was still in the water.
HART: Deliberately to sink a lifeboat?
DOCTOR: Yes, to make sure there were no survivors. What are these markers here?
HART: Those are the last known positions of the missing vessels so far as we can estimate.
(Blythe answers the telephone.)
BLYTHE: Captain Hart's office? Yes. Yes, I see. Hold on. There's a young lady here with two UNIT passes. She wants to know if we've anyone here called the Doctor?

[The Master's cell]

(The Master's television set is like Trenchard's monitor, set into the wall. He switches it on and there is the episode of the Clangers where they find a probe has landed on their planet. The Master whistles along with the puppets. Trenchard enters.)
TRENCHARD: What are you watching?
MASTER: It seems to be a rather interesting extra-terrestrial lifeform.
TRENCHARD: Only puppets, you know. For children.
MASTER: Oh.
(The Master turns off the television.)
TRENCHARD: Well, here's the chart you wanted.
MASTER: Oh, good!
(The Master spreads the chart on the table.)
MASTER: That's right. Thank you. Now.
(The Master plots points on the chart.)
MASTER: You know, Trenchard, a man of your efficiency is really wasted in a job like this.
TRENCHARD: Huh, bit of a comedown in a way, I suppose, but...
MASTER: Never mind. Once our plan succeeds, people will really begin to realise your true worth.
TRENCHARD: Ah. What are you doing?
MASTER: I've just been plotting the sightings of the three sinkings. There, there and there. And it's interesting that right in the middle of them, there's this abandoned sea fort.
(The marked Fort is just off Fortress Island.)
TRENCHARD: Not abandoned any more, old chap.
MASTER: Really?
TRENCHARD: Hart's people are going to use it as a sonar testing station. Contractors are working on the place now.
MASTER: Hmm.

[Sea Fort crew room]

(Inside No Man's Land Sea Fort in the middle of the Solent, two men are playing cards and drinking from cans.)
HICKMAN: How much to see you?
CLARK: A fiver.
HICKMAN: Right.
CLARK: Full house. Kings on twos.
HICKMAN: Oh, that's marvellous, innit. Just marvellous.
CLARK: Come on, it's not your life savings, it's only a couple of quid. I'll give you a chance to get your own back.
HICKMAN: Ah, forget it.
CLARK: What's the matter with you?
HICKMAN: Being stuck out here, I suppose.
CLARK: It's not so bad. Are you sure you don't want another game?
HICKMAN: Do you know, there's something funny about this place.
CLARK: Share the joke.
HICKMAN: Well, the place is deserted, right?
CLARK: So?
HICKMAN: Just the two of us on maintenance?
CLARK: Right.
HICKMAN: Yet I keep getting the feeling I'm being watched.

[Hart's office]

HART: Yes, well, these passes appear to be in order. You may go.
DOCTOR: Go? My dear chap, I don't want to go. I want to visit this fort here.
HART: That fort is being converted for use as a testing station. There's nobody there but a couple of maintenance workmen.
DOCTOR: Nevertheless, it is right in the centre of all the trouble, isn't it? Now if some of your naval bods could get me out there, Captain?
HART: Doctor, I have no authority to provide naval vessels for your pleasure jaunts.
DOCTOR: Look, don't you realise how important this is?
HART: I realise only too well. Three ships have been sunk and many lives have been lost. Now, if you don't mind?
JO: Doctor, I think he wants us to go.
HART: I suggest that you take your theories along to your own people at UNIT and put the whole thing on an official level.
DOCTOR: If Horatio Nelson had been in charge of this operation, I hardly think that he would have waited for official instructions.
HART: Yes, a pretty impulsive fellow, if one can believe the history books.
DOCTOR: History books? Captain Hart, Horatio Nelson was a personal friend of mine. Come on, Jo.

[Sea Fort crew room]

CLARK: Come on, you can't lose anything at draughts.
HICKMAN: There's a jinx on this place. Nothing but trouble since we started repairing the foundations.
CLARK: Forget it. It's not your problem. Black or white?
(There is a noise outside.)
HICKMAN: What's that noise?
CLARK: It's a mermaid. She can't resist us.
HICKMAN: Shut up! There's someone moving about upstairs.
CLARK: It's the wind.
HICKMAN: Fat load of use you are.
(Hickman loads a flare gun.)
CLARK: What are you doing there? Going to send up a distress signal?
HICKMAN: You never know.
(Hickman leaves. He climbs a short ladder to a walkway. Then Clark hears a scream.)
CLARK: Hickman! Hickman?

[Sea Fort]

(Clark climbs the same ladder.)
CLARK: Hickman, where are you?
(Clark finds Hickman lying on a concrete slab, staring at nothing. There is something nearby.)

[Boat]

JO: How do we get onto the fort?
DOCTOR: Up that ladder. Now hold tight, Jo. We're coming alongside now.
(Jo gets on to the ladder first and they climb up past the MOD property No Landing sign.)

[Sea Fort]

(The Doctor and Jo walk down a metal staircase.)
JO: I still say you should have taken Mister Robbin's boat back.
DOCTOR: We will, Jo, we will. And we'll take his motor bicycle back at the same time. Still, now we're here, let's take a look around, shall we?
(A scaly green hand reaches over the side of the boat.)

[Sea Fort crew room]

DOCTOR: Well, somebody's here all right.
JO: But where? Where are they, then?
DOCTOR: This is a big fort, Jo. They must be in some other part of it. Come on, we'll find them.

[Sea Fort]

(As smoke pours out of Robbin's boat, the Doctor and Jo go exploring.)
DOCTOR: There were supposed to be two workmen. They can't just have vanished.
JO: Well, they have, haven't they? Look, Doctor, it's getting dark. Let's get out of here.
DOCTOR: There's plenty of time.
(KaBOOM! They look out of a nearby window at a floating life belt and Robbins' boat for hire notice.)
DOCTOR: It must have been the petrol tank.
JO: But it wouldn't just blow up by itself. Doctor, do you realise we're stranded here!
DOCTOR: Don't worry, Jo. There must be a radio on this fort somewhere. We'll just have to get a message back to shore. Come on.
(A bipedal turtle-faced reptile comes out of the shadows to watch them go. The Doctor and Jo go up that short ladder.)
JO: Look!
DOCTOR: What is it?
(It is Hickman.)
DOCTOR: He's dead, poor chap.
JO: Oh, Doctor, let's get out of here, please.
DOCTOR: All right. Let's find that radio first.
JO: Shush, listen.
(Heavy breathing, and something is approaching. It is Clark armed with a wrench. He raises it to attack.)
DOCTOR: Stop! We're friends! Stop!
(The Doctor grabs Clark's arm and makes him drop the wrench.)
CLARK: Hickman, he's dead! They killed him! Came from the sea. The sea. A sea devil!
DOCTOR: Come on, Jo, quick. Give me a hand.
JO: It's all right.
DOCTOR: We've got to get him into that cabin.
(Jo and the Doctor half-carry Clark back the way they came.)
CLARK: Hickman. Monster.
DOCTOR: Come on. All right.
CLARK: Sea devil.

[Sea Fort crew room]

CLARK: The sea monster.
DOCTOR: Yeah, come on, don't worry. Get yourself down here.
(Clark lies down on the lower bunk bed.)
DOCTOR: That's right. Mind your head. Mind yourself.
JO: That's it.
CLARK: Hickman.
JO: Shush.
DOCTOR: Where's your radio? The radio, where is it?
(Clark points across the room.)
DOCTOR: Over here?
CLARK: Hickman...
JO: Shush.
CLARK: ..ripped it out. They took it away.
DOCTOR: Yes, they certainly did.
(The Doctor opens the First Aid box.)
CLARK: Devil. Sea monster.
JO: Shush.
CLARK: Monster.
JO: Yes, yes, yes.
DOCTOR: Now, listen to me. Take this swab, Jo. Swab his arm. Now, are there are more transmitters on this fort?
CLARK: No, nothing.
DOCTOR: Any transistor radios, that sort of thing?
CLARK: I think so.
DOCTOR: Now, where exactly are these transistor radios?
CLARK: Crew quarters, down the corridor, next deck.
DOCTOR: All right. Thank you. Now don't worry, this is not going to hurt you. Soon feel better. Look after him, will you, Jo?
JO: Yes. Shush. Come on now, try and relax. Come on. That's it.

[Sea Fort]

(The Doctor and a reptile startle each other.)
DOCTOR: Don't be alarmed. I've no wish to harm you.
(The reptile raises its 'hand' which is holding a disc-like device.)
DOCTOR: Now, wait. We must talk.
(A bolt of red energy just misses the Doctor as he ducks. The Doctor runs up the staircase and the reptile follows. The chase goes up and down ladders.)

[Sea Fort crew room]

JO: How do you feel now? Would you like a nice hot cup of tea with some sugar, hmm?
(The Doctor runs in and bolts the door.)
JO: What are you doing?
(The Doctor drags the table over to bar the door.)
DOCTOR: Wire...
(The Doctor find the end of a long wire and goes over to the junction box.)
JO: What is going on?
DOCTOR: Just as I thought. Reptiles, like those creatures in the caves.
JO: The caves?
DOCTOR: It's completely hostile. Here, hang on to this, tight. Hang on.
JO: Right.
(The other end of the wire has crocodile clips.)
JO: Well, now what are you doing?
(The Doctor fastens the clips to the door bolts then returns to the junction box.)
DOCTOR: Those creatures can cut through anything. Rock, metal, anything.
JO: Look!
(The metal door is starting to melt. A green hand reaches through the hole and gropes for the bolts. The Doctor throws the power switch and it screams, pulling its hand back. He turns the power off again. The Doctor pulls the table back and unbolts the door.)
JO: Where are we going?
DOCTOR: We've got to get after that creature. Now, come on.
(They chase it through the fort until it jumps out of a broken window into the sea.)

[Hart's office]

(WRNS Blythe is on the phone.)
BLYTHE: Keep trying.
(Hart enters.)
HART: Morning, Blythe.
BLYTHE: Good morning, sir.
HART: Anything in?
BLYTHE: We've had this report from the civilian police, sir. That man who was here yesterday trying to get over to the fort, seems to have disappeared with the boat he came in.
HART: Oh, no.
BLYTHE: He and the girl were seen heading out to sea yesterday afternoon. There's been no sign of them since.
HART: Well, get onto the fort and see if they've wound up there.
BLYTHE: I've already done that, sir. The fort just wasn't answering. I can't raise them at all.
HART: Well, we'd better take a look around. Get me Air Sea Rescue.

[Sea Fort crew room]

(The Doctor is constructing a transmitter from the radios.)
JO: Doctor?
DOCTOR: Mmm?
JO: Those things that attacked us. You said you'd seen something like it before.
DOCTOR: Something very similar, certainly. They emerged from some caves in Derbyshire.
JO: The Silurians, wasn't it? The Brigadier was telling me.
DOCTOR: That's a complete misnomer. The chap who discovered them must have got the period wrong. No, properly speaking, they should have been called the Eocenes.
JO: That was that race of super reptiles that had been in hibernation for billions of years, wasn't it?
DOCTOR: That's right, and if you want my opinion, there's another of their colony right here beneath us.
JO: Well, something seems to have woken them up.
DOCTOR: Probably the rebuilding of this fort.
JO: But I thought you said they lived in caves?
DOCTOR: Well, this is a different species, completely adapted to life underwater.
JO: And they've been sinking the ships?
DOCTOR: Very likely.
JO: Why are they so hostile? What have we done to them?
DOCTOR: Well, they still think of Earth as their planet, Jo, and they want it back. As far as they're concerned, man is just an ape who got above himself. Right, I think that should do it. Let's have another go. Hello, hello. Mayday, Mayday, Mayday! This is, er, this, er, this is. What is this? What's our call sign?
(Jo reads the note on the wall above where the radio used to be.)
JO: Oscar Bravo Tango Seven Four.
DOCTOR: Hello, Mayday, Mayday, Mayday, this is Oscar Bravo Tango Seven Four. We are stranded on this fort and have a wounded man here. Can you send immediate assistance? Can you hear me? Can you hear me? Over.
JO: Oh Doctor, you don't think you'll get through to anybody on that old lash-up, do you?
PILOT [OC]: Hello, Oscar Bravo Tango, I am receiving you loud and clear. I am about to land. Over.
(Helicopter rotors can be heard overhead.)
JO: It works!
DOCTOR: Hello, Oscar Bravo Tango speaking. Who are you? Who are you? Over.
(Jo runs outside to look through a window.)
JO: It's a helicopter!
DOCTOR: Yes. Well, though I say so myself, I think that's a remarkably efficient piece of work.
(And the set goes Bang!)

[Naval base]

(A prison guard drives Trenchard into HMS Seaspite and parks up. Actually HMS St. George, Portsmouth)
TRENCHARD: You can go to the Petty Officer's mess. I'll send for you later.
GUARD: Very good, sir.
(The guard leaves. Trenchard looks around then knocks on the side of the car and walks away. The Master comes out from underneath a rug in the back dressed in a Lieutenant Commander's uniform. A squad of ratings marches past.)
CPO: Squad, eyes right!
(The Master salutes.)
CPO: Eyes front! About turn! Squad...

[Hart's office]

HART: All right then, Doctor, let's assume that I accept the existence of these Sea Devils. What do you want me to do?
DOCTOR: Well, to begin with, we must make every effort to make contact with them.
HART: But you claim that they're responsible for sinking the ships.
DOCTOR: It may still be possible to find a peaceful solution. We're not dealing with animals, Captain Hart, we're dealing with intelligent beings.
(There is a knock on the door and Trenchard enters.)
TRENCHARD: Have you got a minute, old chap? Ah, thanks very much. Wanted a word with you about the golf tournament. Good heavens!
DOCTOR: Colonel Trenchard.
TRENCHARD: Doctor. Miss Grant. Thought you two'd left the island yesterday.
JO: Well, we didn't quite manage to get away.
(The Master has found the base stores and is collecting supplies.)
TRENCHARD: Er, sorry to butt in, John, old man, but it's about the weekend. We are rather relying on you, you know.
HART: Now, don't worry, George. If I can't make the tournament, I'll let you know in plenty of time.
TRENCHARD: Yes, but you do understand I don't want you to feel under any pressure about this. If you want to drop out, I suppose I could rope in old Harry.
HART: Well, perhaps that's for the best. Now, if you don't mind, George?
TRENCHARD: At the same time, I don't want you to miss the game.

[Naval base stores]

(The Master is putting the items into a duffel bag when the Chief enters.)
SMEDLEY: I'm sorry, sir, but should I know you?
MASTER: You certainly should, Chief. Had you not been warned of my coming?
SMEDLEY: No, I'm afraid not, sir.
MASTER: Special audit, Ministry of Defence.
SMEDLEY: Special audit, sir?
MASTER: Yes, the items in this bag here are defective. Did you realise that you were carrying defective supplies here, Chief?
SMEDLEY: Look, I'm sorry, sir, but do you mind if I see your pass, please?
MASTER: Captain Hart's preparing it right now. He'll be bringing it down right away.
SMEDLEY: I see, sir. Well then, you won't mind if I just phone and double check then, will you.
MASTER: What exactly are you suggesting, Chief?
SMEDLEY: I'm not suggesting anything, sir. I'm just obeying orders.
MASTER: You will obey my order, Chief Petty Officer!
SMEDLEY: Your order, sir?
(The Master fixes Smedley with his Look.)
MASTER: You will obey me. You have seen my pass and it is quite correct.
SMEDLEY: Your pass...
MASTER: You have seen my pass.
SMEDLEY: No, I've got to phone and check.
(So the Master gives him a chop to the back of the neck, picks up the bag and leaves.)

[Hart's office]

TRENCHARD: Goodbye, Miss Grant. It's been a great pleasure to see you again.
JO: Goodbye, Colonel.
TRENCHARD: Well, I'll, er, I'll be pushing off then. Oh, thanks very much.
HART: I'll be in touch, George.
TRENCHARD: Yes.
(Trenchard leaves.)
HART: Now then, Doctor, where were we?
DOCTOR: Where were we indeed? Ships must be kept away from this area.
HART: Doctor, those are major shipping lanes. We'd have protests from all over the world.
DOCTOR: You'll have even bigger protests if ships go on sinking.
HART: And even if we do declare it a prohibited area, how are we going to enforce it?
(Jo looks out of the window and sees something that surprises her.)
HART: You know what happens in the English Channel. Trinity House marker buoys are ignored half the time.
DOCTOR: You'll just have to patrol the area, won't you?
HART: What are we supposed to do?
DOCTOR: You don't seem to realise how dangerous...
(Jo is looking out of the window.)
JO: Doctor!
DOCTOR: What?
JO: Doctor, come here!
DOCTOR: Jo, please, not now.
HART: Don't you believe it.
JO: Doctor, it's the Master!
DOCTOR: What? Where?
JO: Down...
(Just two ratings walking through now.)
JO: But it was him. Look, I know it was.
DOCTOR: Captain Hart, I suggest that you order a full security alert immediately.
HART: Would you mind telling me what this is all about?
DOCTOR: Miss Grant has just seen a very dangerous criminal on your base.
HART: Doctor, I've been very patient with you, but if I thought...
BLYTHE: Sir, someone's been found unconscious in the sonar stores.
DOCTOR: Come on.

[Naval base stores]

SMEDLEY: I don't know. He was taking equipment, sir. Said he was doing some special audit. Well, I went to phone up to check and that's when he hit me.
DOCTOR: What did this officer look like?
SMEDLEY: About my height. He was dark and he had a short beard.
JO: You see? The Master.
HART: Who is the Master?
JO: How did he get in here? He's supposed to be locked up.
DOCTOR: Trenchard.
JO: What?
DOCTOR: Well, don't you see? He arrived just before this happened and he left a few moments ago.
JO: Of course. All that silly talk about a golf tournament.
HART: Are you suggesting that George Trenchard is mixed up in all this?
DOCTOR: Yes, I certainly am. Captain Hart, can you lend me some transport?
HART: Well, of course I can, but what's it all about?
DOCTOR: No time to explain now. Come on, Jo.

[Governor's office]

(The Doctor and Jo arrive at the castle in a Royal Navy Land Rover. The Doctor actually shows his own pass to the guards. Trenchard is practising his putting, and boy does he need the practise. There is a knock at the door.)
TRENCHARD: In conference.
(The Doctor enters, followed by Jo.)
DOCTOR: Colonel Trenchard.
TRENCHARD: Hello, old chap. What are you doing here?
DOCTOR: I've reason to believe that your prisoner has escaped.
TRENCHARD: Nonsense!
DOCTOR: Is it?
TRENCHARD: See for yourself.
(Trenchard turns on the monitor. The Master is reading a book.)
TRENCHARD: There you are, you see? Safe and sound.
JO: Well, he may be here now, but half an hour ago he was at the naval base.
TRENCHARD: Impossible. A clear case of mistaken identity.
(The Doctor gives him a Look of his own.)
TRENCHARD: I'll tell you what, though. I'll go and check the guards myself.
DOCTOR: Yes, you do that.
TRENCHARD: Yes.
(Trenchard leaves. A moment later Jo checks that the corridor is empty.)
JO: All clear.
DOCTOR: Try and get an outside line. No, they're both completely dead.
(The Master climbs on a chair and removes a grille from in front of a security camera. He puts a cloth over the lens and replaces the grille.)
DOCTOR: I want you to take the jeep, go down to the naval base and call UNIT. Tell them that Colonel Trenchard and his entire staff are to replaced immediately.
JO: But, Doctor...
DOCTOR: No buts, Jo. Just do as I ask. I'll stay here and keep an eye on him. Now, you hurry.

[The Master's cell]

(A guard enters.)
MASTER: Ah, I think there's something wrong with the air conditioning in here. Now, that grille seems to be blocked.
(The guard turns and looks up, and the Master hits him on the back of the head, double fisted, and takes his gun.)

[Castle entrance]

(Jo goes up to the guard who is holding the car keys. He puts them in his pocket.)
JO: The keys! I've got to get back to the naval base. It's urgent!
BARCLAY: Sorry, Miss. Orders. Take her back inside.
(Barclay turns Jo around so she elbows him in the stomach and pushes him into his colleague, then runs.)
BARCLAY: Well, don't just sit there. Get after her!

[The Master's cell]

The door is wide open and there are no guards. The Doctor stands in the doorway.)
MASTER: Why, Doctor, so you came for a chat.
DOCTOR: Been out for a little jaunt, have you?
MASTER: I beg your pardon?
DOCTOR: Why did you go to the naval stores and steal those electronic spares?
MASTER: How could I possibly go anywhere? You know very well that I'm a prisoner.
DOCTOR: You've got some sort of hold over Colonel Trenchard. What's going on?
MASTER: I can see that I shall have to tell you everything.
(The Master produces the guard's gun from under his newspaper.)
DOCTOR: Good afternoon!
(And shuts the door.)

[Outside the Master's cell]

(The Master opens the door and steps out.)
DOCTOR: Akidai!
(And kicks the gun out of the Master's hand. The Master grabs a foil from a rack on the wall.)
DOCTOR: Like that is it?
(And takes a foil from another rack. The two foes fence. The Doctor pushes the Master back, and he stumbles, so the Doctor disappears behind a curtained doorway. The Master starts slashing at the fabric.)
DOCTOR: I wouldn't do that if I were you. That's government property.
(The Doctor has come round behind him. They cross swords again and the Master pushes the Doctor into the cell.)

[The Master's cell]

(Where the Doctor falls back across the table, dodges the Master's attacks then disarms him, holding him pinned by the tip of his foil.)
DOCTOR: I always find that violent exercise makes me hungry. Don't you agree?
(The Doctor takes a bite from one of the Master's sandwiches.)
MASTER: Then you'd better enjoy your meal, Doctor, because it might be your last.
DOCTOR: Oh, you think so?
(The Doctor returns the Master's foil. The Master drives him back into the chair.)
MASTER: You're good, Doctor, but you're not good enough.
DOCTOR: Ah, but you haven't seen the quality of my footwork yet!
(The Doctor kicks the Master back over the table. Disarmed again, the Master stays on the floor. Trenchard enters with a guard.)
TRENCHARD: What's happened?
MASTER: I was defending myself. This man came here to kill me.
TRENCHARD: Be so good as to explain yourself, Doctor.
DOCTOR: Only a complete fool would listen to such an accusation. Though I suppose in your case...
TRENCHARD: Don't speak to me like that. I shall have a full enquiry into the whole thing. Meanwhile, consider yourself under arrest. Take him to my office immediately.
DOCTOR: Oh, don't be absurd, man.
(Jo hides behind some brambles as a bunch of guards run past, then sets off again.)
TRENCHARD: If you attempt to escape, the guards will shoot to kill.
(The Doctor is manacled and in the chair. The Master is back in his usual suit. The guard unfastens one cuff...)
DOCTOR: How very kind of you.
(..then pulls the Doctor's arms behind the chair and fastens it again.)
DOCTOR: How very unkind of you.
TRENCHARD: Right, I'll leave you to have your little chat. There will be a guard outside at all times.
DOCTOR: I'm very relieved to hear it.
(Trenchard and the guard leave. The Master shuts the door.)

[Hart's office]

HART: I can't give you much to go on, I'm afraid, but I believe there's something down there. Your submarine's fitted with the new experimental sonar. It'll give you a chance to try it out.
(The submarine Commander sports a 'full set' of whiskers.)
RIDGEWAY: What are we looking for, sir?
HART: I wish I knew. The man we took off the fort was babbling something about sea devils.
RIDGEWAY: Don't you think this is getting a bit out of hand, sir? Ships have vanished at sea before.
HART: To be exact, seventy in the last ten years. But we've lost three, all in the same area, in the last few weeks.
RIDGEWAY: We'll do what we can to find your sea devils, sir.
HART: I want you to signal me a full report the moment you resurface.
RIDGEWAY: Yes, sir.
HART: All right, carry on.
RIDGEWAY: Thank you, sir.
HART: And good luck.
RIDGEWAY: Thank you, sir.
(Ridgeway leaves.)
BLYTHE: Excuse me, sir?
HART: Yes?
BLYTHE: I was just wondering about Miss Grant and the Doctor. Shouldn't they be back by now?

[The Master's cell]

(Jo hides by the sandbags of a firing range as a group of guards drive past in a 2CV. She tries an old wooden door in the castle wall, but it stays shut so she moves on.)
MASTER: You realise, of course, that I could kill you here and now?
DOCTOR: And how would you explain that away to Colonel Trenchard? I'm hardly in a position to attack you, now am I?
MASTER: Do you really think I care what Trenchard thinks?
DOCTOR: Whatever you're up to, you still need Trenchard's cooperation. You're still a prisoner here, you know.
MASTER: My dear Doctor, I can walk out of here any time I choose.
DOCTOR: Then why don't you?
MASTER: Because this place makes a good base for my operations. You see, I'm planning to contact our reptilian friends.
DOCTOR: How do you know about them?
MASTER: Oh, from the Time Lords' files.
DOCTOR: More stolen information?
MASTER: Naturally.
DOCTOR: Well, why do you want to contact them?
MASTER: Those reptiles, Doctor, were once the rulers of this Earth. And with my help, they can be so again.

[Naval base radio room]

(The submarine is making good speed.)
RIDGEWAY [OC]: Entering the specified zone now, sir. About to dive.
HART: Very well. Standing by for your report. Carry on.

[The Master's cell]

DOCTOR: I still don't see why you want to help them. What can you possibly gain?
MASTER: The pleasure of seeing the human race exterminated, Doctor. The human race of which you are so fond.

[Submarine]

(The submarine is now fully submerged.)
RIDGEWAY: Keep fifty feet.
MITCHELL: Aye, aye, sir. (into com) Stand by to blow Q.
RATING [OC]: Stand by to blow Q.
MITCHELL: Blow Q.
RATING [OC]: Blow Q.
RIDGEWAY: Up periscope. Right, Number One, stand by to start your sonar watch.
MITCHELL: Aye, aye, sir. Er, what are we looking for, sir?
RIDGEWAY: I don't know. Maybe we'll know when we find it.
MITCHELL: Sir.

[The Master's cell]

DREW: The governor wants to see you, sir.
MASTER: In a moment.
DREW: He wants to see you now, sir.
DOCTOR: Better run along, old chap. You're still a prisoner here, you know.
(The Master picks up his device.)
DOCTOR: You'll never get it off the ground.
(The Master leaves and the Doctor starts to test how the chain of his manacles has been twisted around the frame of the chair. Outside, Jo runs around the castle, looking in windows until she spots the Doctor. She taps on the glass behind the iron bars and gestures to him, indicating that she has to carry on finding a way in, and he is to wait five minutes then start making a lot of noise. The Doctor mouths 'okay' and looks at the clock. 2:07.)

[Governor's office]

TRENCHARD: I can't keep it up, you know. The lies I've told... How long before that device of yours is ready?
MASTER: Oh, just a few hours now.
(Jo carries on round the building until she finds a sash window which has been left slightly open.)
TRENCHARD: What is exactly is it?
MASTER: It's a perfect replica of the communications device used by the enemy agents. We are going to use it to lure them into a trap.
(Jo crawls through the window into a small room then out across a small, cluttered courtyard.)
Just think of it, Trenchard. You will be responsible for exposing some of the most dangerous saboteurs this country has ever known. I think you'll find that a grateful government will give you anything that you ask for.
TRENCHARD: Oh, don't want any reward, of course. Just doing my duty.

[The Master's cell]

(It is now 2:13.)
DOCTOR: Anyone out there?

[Outside the Master's cell]

DOCTOR [OC]: I said, is there anyone out there?
DREW: Please be quiet, sir.
DOCTOR [OC]: Look, guard, I want to talk to you. I said I want to talk to you!
(Jo peeks round the corner.)

[The Master's cell]

DREW: What's all the noise about, sir?
DOCTOR: How much longer am I going to be kept chained up like this?

[Outside the Master's cell]

(Jo creeps down some stairs towards the open door.)
DOCTOR [OC]: What about the Geneva convention?
DREW [OC]: You'll have to stay here till someone tells me different, sir.
DOCTOR [OC]: What about some food, then? I'm sure they didn't tell you to starve me to death.
DREW [OC]: You'll be fed when the time comes.

[The Master's cell]

(Jo enters unseen and hides behind the door.)
DOCTOR: You tell Colonel Trenchard that I want to see him straight away. He's got no right to keep me here like this.
DREW: Look, sir, you're a lot better off here than in one of the cells, so please be quiet, sir.
(Drew leaves and Jo waves at the Doctor then checks his manacles.)
DOCTOR: (silent) You'll find tools over there.
(Jo gets the small screwdrivers from the Master's table and starts picking the lock.)

[Governor's office]

TRENCHARD: This Doctor fellow, have you finished with him?
MASTER: For the time being, yes. Oh, by the way, what about the girl? Have they caught her yet?
TRENCHARD: Oh, grounds are very large, you know. Only a matter of time, though. She can't get away.
MASTER: I hope you're right. Er, it might be better if one of the guards were to take me back.
TRENCHARD: Huh? Oh, yes, of course! Er, must keep up appearances, what? Guard?

[The Master's cell]

(Jo is hiding behind the door again.)
DOCTOR: Guard. Guard! I want to talk to you!
(Drew enters.)
DREW: What's wrong now, sir?
DOCTOR: These handcuffs. They're far too tight. They're killing me.
(Jo kneels down directly behind Drew.)
DREW: I'm under strict instructions, sir, that they're to be kept on...
(The Doctor butts Drew, sending him tumbling over Jo, who then chops him across the throat. The Doctor unwinds the chains from the chair.)
DOCTOR: After you.
JO: No, after you.
DOCTOR: No, no. After you.

[Submarine]

(The sonar is operating.)
RIDGEWAY: Anything, Number One?
MITCHELL: Er, no, sir. Nothing. Nothing at all.
RIDGEWAY: Well, keep trying, old chap.
MITCHELL: Sir.
(There is a return ping.)
MITCHELL: Er, we have a contact, sir.
(The sonar goes to simultaneous pings and the operator, Lovell, rips off his headphones.)
RIDGEWAY: What the blazes is that?
LOVELL: It's gone crazy, sir.
RIDGEWAY: Get on to the sonar maintenance.
MITCHELL: Aye, aye, sir.
LOVELL: It's packed up, sir.
MITCHELL: It's gone dead, sir!
(Then the lights go out.)
RIDGEWAY: What the devil's going on?
ENGINEER [OC]: Manoeuvring room here, sir. Loss of essential power supplies.
MAN [OC]: Reporting loss of essential power supplies.
MAN 2 [OC]: Loss of essential supplies.
MAN 3 [OC]: I repeat...
(The submarine hangs dead in the water.)

[The Master's cell]

(Trenchard looks in to see the Master holding the manacles and cradling Drew's head in his lap.)
MASTER: It would appear that Miss Grant has succeeded in releasing the Doctor.
TRENCHARD: This is appalling! It'll ruin everything!
MASTER: Exactly. That's why you've got to find them!

[Submarine]

(The boat is sinking.)
MITCHELL: It's no good, sir. There's absolutely nothing wrong with the engines. We've run a complete check on them.
RIDGEWAY: And we're still going down.
(She hits bottom.)
MITCHELL: What do we do now, sir?
RIDGEWAY: Keep working on the engines.
MITCHELL: There's nothing wrong with them, sir. There's nothing wrong with any part of this boat. We've checked everything.
RIDGEWAY: Then check again.
(Something starts banging on the hull.)
MITCHELL: Divers?
RIDGEWAY: That's impossible.
MITCHELL: There's something out there, sir.
RATING [OC]: Forward section here, sir. We're being attacked.
(Men shouting in the background.)
RIDGEWAY: This is the captain. What's happening?
RATING [OC]: Someone's coming in, sir, through the escape compartments.
RIDGEWAY: Shut off forward and aft escape compartments.
MITCHELL: Aye, aye, sir.
RIDGEWAY: What's happening, man?
RATING [OC]: They're coming in, sir! They're... Argh!

[Castle grounds]

(The Doctor and Jo run down a slope. Nearby is a bayonet practice area. A guard watches them go.)
BARCLAY: Ground to control. Subjects entering sector twenty seven.

[Governor's office]

TRENCHARD: Yes, yes, all right.
(Trenchard puts the phone down.)
TRENCHARD: They're making for the beach, towards the minefield.
MASTER: No doubt they're trying to rejoin their associates at sea.
TRENCHARD: Right. We must head them off.
MASTER: No. Let them get to the beach.
TRENCHARD: But we've got to catch them.
MASTER: We shall. This device is now ready for testing. We shall use it to trap them all together.
(The Master switches on his device. A small dish starts spinning, broadcasting its signal.)

[Cliff and Beach]

(The Doctor and Jo run across the beach but are cut off by guards in a 2CV. To their right is a cordoned off area labelled Danger Minefield. On the cliff, the Master switches on his transmitter and points it at the waves. A reptile like the one on the old Fort emerges from the surf. The guards turn.)
JO: Doctor, look!
(Up on the cliff.)
TRENCHARD: What is it?
MASTER: One of the creatures that have been destroying the ships.
TRENCHARD: You told me it was enemy agents. Why didn't you tell me the truth?
MASTER: If I had, would you have believed me?
(On the beach, the guards are staring at the reptile.)
DOCTOR: There's only one thing for it. We'll have to go through the minefield.
(The reptile uses its weapon and kills one guard, then another. A gunfight starts. The Doctor throws himself across the first roll of barbed wire to flatten it and let Jo across, then the second and into the minefield proper.)
JO: We'll get blown up.
DOCTOR: No, don't worry. My sonic screwdriver. It converts into rather a good mine detector.
(The screwdriver pings like sonar. This attracts the reptile who has now killed all the guards.)
MASTER: Stupid beast. Why doesn't it attack them?
(The Master alters the amplitude of the transmission and the reptile heads for the minefield. The Doctor and Jo reach an area where an unwary gull has previously set a mine off.)
JO: Doctor, it's following us!
(The reptile comes through the gaps made by the Doctor.)
JO: Doctor!
DOCTOR: Relax, Jo, relax.
(The Doctor adjustments the screwdriver and aims it back towards the reptile. A nearby mine goes Bang! then another and another. It takes a fourth and fifth to sent it screaming back to the waves. The Doctor retunes again.)
DOCTOR: Right, follow me.

[Naval base radio room]

HART: Anything from the sub yet?
BOWMAN: It's no good, sir, there's nothing.
HART: They had instructions to surface over an hour ago.
BLYTHE: Maybe they've found something, sir. Perhaps they're still investigating.
HART: If they haven't surfaced by now, then something must be stopping them. All right, submiss procedure. Alert submarine command. We'll set up a full-scale search right away.

[Submarine]

RIDGEWAY: Radio Captain Hart the moment you surface. Tell him we're immobilised on the sea bed by some unknown force and intruders have broken through the hull.
SUMMERS: Aye, aye, sir.
(Summers is in an immersion suit, ready to escape the seabed.)
RIDGEWAY: You've checked your R/T?
SUMMERS: Yes, sir.
RIDGEWAY: All right, carry on. Good luck.
MITCHELL: Something's happening to this door, sir. It's getting hot.
RIDGEWAY: Right, small arms, Number One.
MITCHELL: Aye, sir.
(Mitchell unbars and unlocks a cupboard.)
SUMMERS: Forward hatch is jammed, sir.
RIDGEWAY: All right, Summers. Johnson, here. Petty Officer, here.
(Small automatic weapons are handed out from the cupboard as a bulkhead starts to melt.)
RIDGEWAY: Right, take cover.
MITCHELL: The door's going!
RIDGEWAY: All right, Number One. Hold your fire until we see what they are.
(A reptile comes through the molten remains of the bulkhead.)

[The Master's cell]

TRENCHARD: You've misled me all along. You said it was spies, saboteurs. You said we'd catch them.
MASTER: Look, if I had talked to you about sea monsters, would you have believed me?
TRENCHARD: I've risked everything to help you and you've lied to me.
MASTER: I had to lie. Now sit down, Trenchard. Sit down and listen to me. That creature that you saw is one of a race of intelligent reptiles that has a deadly hatred of mankind. Now, somehow, they've established themselves in the sea, but now they intend to emerge and conquer the Earth.
TRENCHARD: What? We must warn the authorities at once!
MASTER: No, no, no. Premature action would ruin everything.
TRENCHARD: What else can we do?
MASTER: Wait until this device of mine is perfected, and then tell the authorities.
TRENCHARD: What about the Doctor? He'll report to UNIT.
MASTER: You must trust me a little longer. I assure you all your troubles will soon be over.

[Hart's office]

HART: I'm sorry if I seem to be repeating myself, Doctor, but I don't believe a word of it!
DOCTOR: Well, I can assure you we didn't walk ten miles across open countryside just to tell you fairy stories.
HART: Monsters coming out of the sea.
JO: But it's different this time. Everybody saw it. Even Trenchard and the guards.
HART: And you think Trenchard will confirm your story?
DOCTOR: I doubt it. The Master's got some sort of hold over him.
JO: The Doctor's seen these creatures before.
HART: Oh, I'm quite sure he has, Miss Grant.
JO: In some caves in Derbyshire. You see, they want to take over the Earth...
HART: Oh, really, Miss Grant, if you think for one moment I'm going to believe...
JO: Well, re-take if you like, and what they're going to do is...
DOCTOR: All right, Jo, all right, all right. Let me deal with the explanations. Look, it's like this
(Blythe enters with a plate of sandwiches for Jo.)
BLYTHE: Only cheese, I'm afraid. The best the steward could do.
JO: Oh, that's super. Thanks very much.
DOCTOR: For heaven's sakes, Jo. What do you think this is, a picnic?
DOCTOR: All right, well let's forget about the Sea Devils. What about Trenchard trying to take us prisoners then?
(The Doctor eats Jo's sandwiches.)
HART: Well, I only have your word for that, haven't I?
DOCTOR: All right, what about the theft of your electronic spares? Surely you'll agree that happened?
HART: Since I was here at the time, yes.
JO: The Master stole those parts to make his calling device, and...
HART: His what?
DOCTOR: Well, he's developed some way of communicating with them. Probably a ultra-high frequency sonic beam. These are rather good. Want one?
HART: No, thank you.
DOCTOR: Sandwich?
BLYTHE: Thank you.
JO: Doctor!
DOCTOR: Oh, I'm so sorry.
(Jo is left with the lettuce garnish. The telephone rings.)
BLYTHE: Captain Hart's office? Oh, I see. Yes, yes, I'll tell him. They've had to abandon the search, sir. They'll start again at first light.
(Blythe leaves.)
DOCTOR: How overdue is the submarine?
HART: Four hours.
DOCTOR: It should never have been sent, you know. They were bound to presume it was hostile.
HART: Kindly leave the naval side of the operation to me, Doctor.
DOCTOR: Captain Hart, you are dealing with a situation completely outside of your own experience. And if you won't let me help you...
HART: All right then, Doctor. What do you want me to do?

[The Master's cell]

(The Master has his device running on yet another frequency, that sounds like very speeded up speech. Then he switches off, taps at a bank of eight keys and switches on again. Off, more keying, and Trenchard enters.)
TRENCHARD: That thing working all right?
MASTER: It still needs a few minor adjustments.
(The device emits more speeded up speech and the Master unplugs it.)
TRENCHARD: What was that?
MASTER: Just random feedback. It's nothing important.
TRENCHARD: Sounded like some sort of message.
MASTER: Look, Trenchard, I am trying to carry out a very difficult and complex task here, and I can't work if I'm being continually interrupted.
TRENCHARD: I'm terribly sorry, old chap. I'll leave you to it.
MASTER: Thank you.
TRENCHARD: Yes.
(Trenchard leaves. The Master plugs the machine back in and the message comes tumbling out. He smiles. Under cover of darkness, six reptiles are walking through the surf to the shore. Further out, six more are emerging from the depths.)

[Governor's office]

TRENCHARD: (into phone) I tell you I must speak to the Minister. It's most important. When do you expect him back? No, I can't tell you what's wrong. The security of the nation is at risk. Oh, very well, I'll hold on, but please hurry!
(The reptiles are in the building and killing guards.)
TRENCHARD: (into phone) No, it can't wait till the morning. Oh, you'll have to interrupt his meeting. This is a matter of national urgency. Oh, very well, as soon as he's free then. But if there's any unnecessary delay, believe me, you'll answer for it.
(Trenchard unlocks a drawer in his desk and takes out his service revolver, checking that it is loaded.)

[Castle]

(A patrol of two guards encounter two reptiles in a corridor, and one man manages to set off the alarm. Guards and Trenchard run through corridors, guns at the ready. Reptiles kill two guards and make their way through the building to the Master's cell. Trenchard comes across Drew firing at something.)
TRENCHARD: What's happening, man?
DREW: They're all over the place, sir! They killed most of the lads!
TRENCHARD: Who? Who's attacking us?
DREW: Lizards, sir. Like that thing we saw on the beach. Come on, sir. They were after me.
TRENCHARD: Pull yourself together, man. Have you sent for help?
DREW: It's no good, sir.
TRENCHARD: There's a direct line to Whitehall in my office. Use that.
DREW: Why can't you, sir?
TRENCHARD: I shall attend to the security of my prisoner. Go on, man. Move!
(Drew leaves. Trenchard faces three reptiles and empties his revolver into one of them, which clutches its chest. The clock on the wall says it is just after 9.00 when the Master stops sending his message, and the three reptiles enter his cell. Trenchard lies dead on the floor outside.)

[Outside the Castle entrance]

(Two Navy Land Rovers arrive with Hart, the Doctor and Jo, and armed Marines.)
HART: Come on. Follow me.

[Castle]

(The group come across a dead guard.)
HART: Doctor!
(He has spotted Trenchard's body.)
HART: I don't understand why.
DOCTOR: The Master had no further use for him, that's why.
HART: But why did he help the Master in the first place?
DOCTOR: What would you say was Trenchard's strongest characteristic?
HART: Oh, I don't know. Patriotism, I suppose.
DOCTOR: Exactly. And the Master used that patriotism as a weapon.

[Naval base radio room]

BOWMAN: Well, they're definitely getting an echo and the object's moving.
BLYTHE: I see.
HART: What is it, Bowman? Have they re-established contact?
BOWMAN: It's a message from one of the search vessels, sir. They are getting an echo.
DOCTOR: The submarine?
BOWMAN: Yes, it's moving towards the fort now. Moving at about thirty knots.
HART: Depth?
BOWMAN: Steady at one five zero feet.
DOCTOR: The fort... Look, Captain Hart, can you lay on a diving vessel?
HART: Yes, the Reclaim's standing by on the search. But why?
DOCTOR: I want to inspect the sea bed at the base of that fort.

[HMS Reclaim dive control]

(The Doctor and Jo are ferried out in a launch to the Royal Navy's diving and search ship, A23, who sadly no longer exists. The Doctor is piped aboard. and they go down to the divers section where the tanks and dry suits are kept.)
HART: All pre-dive checks completed?
WATTS: Yes. sir.
HART: Doctor, are you quite sure you want to go through with this?
DOCTOR: Yes, positive.
HART: Ready to lower the observation chamber?
WATTS: Yes, sir. The crew is standing by. We'll send a man down with him.
HART: Good.
DOCTOR: If you don't mind, I'd rather go down on my own.
HART: Well, I presume you're a trained diver in addition to your other accomplishments then, Doctor?
DOCTOR: Naturally. What's more, I know these creatures. I've encountered them before so I know what I'm looking for.
HART: All right, carry on.
WATTS: Aye, aye, sir.
JO: Doctor?
DOCTOR: What is it, Jo?
JO: Is it really necessary for you to go down?
DOCTOR: How else am I going to make contact?
HART: Doctor?

[HMS Reclaim]

(The diving bell is waiting, hanging from its crane on deck.)
HART: Well, good luck, Doctor.
DOCTOR: Thank you, Captain Hart.

[Diving bell]

(The Doctor climbs up into the bell.)
C.P.O: Everything okay, sir?
DOCTOR: Yes, thank you, Chief.

[HMS Reclaim]

WATTS: Test the links.
(The crew make their final checks and then the crane hoists the bell over the side.)
WATTS: Pull up the links. Carry on lowering.
(The bell enters the water.)
SAILOR: Twelve feet.
OFFICER: Carry on lowering.

[HMS Reclaim dive control]

HART: Let me speak to him. How's it going, Doctor?
DOCTOR [on monitor]: Splendid, thank you. A most interesting trip.
HART: You'll reach seabed in a few minutes. Tell us immediately if anything goes wrong.
DOCTOR [on monitor]: Don't worry. I'll be all right.
HART: You have reached seabed. Are you all right, Doctor?

[Diving bell]

DOCTOR: Yes, I'm fine, thank you.
(The Doctor peers out of a porthole.)
DOCTOR: Hang on a minute!
(And a reptile peers in.)

[HMS Reclaim dive control]

HART: Are you all right, Doctor? Shall we bring you up?
DOCTOR [on monitor]: Definitely not! I think I've just... (static)
HART: Bring him up!
WATTS: Start winches! Hoist SCC!

[HMS Reclaim]

OFFICER: High enough. Stop the lift.
(The bell is pulled into the deck and locked off in its original position. Jo looks inside the bell. It is empty.)
JO: He's gone!
(Somewhere else, a much smaller and very alien diving bell is being lowered in the Sea Devil's base. Watching the operation is one reptile wearing a fishnet cloak as well as the tunic. It gestures and a plug is removed from the side of the bell, dragging cables out with it, and revealing the Doctor's face.)

[Hart's office]

(A man in camel hair coat and bowler hat enters.)
WALKER: Good morning, my dear. Captain Hart here?
BLYTHE: No sir, he's at sea.
WALKER: Well, I suppose that's the right place for a sailor, eh? What's your name?
BLYTHE: Blythe, sir.
WALKER: Walker. Parliamentary Private Secretary. Any chance of any breakfast?
BLYTHE: I'll call the steward, sir.
WALKER: Excellent!

[Naval base radio room]

WALKER: And, er, who are you?
BOWMAN: Leading Telegraphist Bowman, sir.
WALKER: Jolly good. Er, nothing very elaborate, my dear. Just eggs, bacon, toast, coffee. Oh, and a little rough-cut marmalade, if they've got it. How long is he likely to be? Captain Hart, I mean.
BLYTHE: I don't know, sir.
WALKER: Oh, well, now, I tell you what. You get him on your jolly old wireless and ask him to come over here at the double, will you?
(Walker gives Blythe his hat and coat, and goes back into the office.)
BLYTHE: Send a signal to Captain Hart. Tell him that a Mister Walker is here to see him.
WALKER: Parliamentary Private Secretary.
BOWMAN: Er, aye, aye, sir.

[Hart's office]

BLYTHE: I'll call the steward.
WALKER: Ah, and get me the morning papers, will you, there's a good girl.
BLYTHE: If I may ask, sir, what is the purpose of your visit?
WALKER: Why, all those ships sinking. I've come down to clear it up for you. The Minister's put me in full charge.

[Sea Devils base]

SEA DEVIL: This is our planet. My people ruled the Earth when man was only an ape.
(The Doctor is out of the bell.)
DOCTOR: Your people went into hibernation and abandoned Earth to its fate.
SEA DEVIL: Our astronomers predicted that a great catastrophe would end all life on the face of the Earth.
DOCTOR: Yes, but the catastrophe that you predicted never happened. And the apes that you left behind on the surface to die became man.
SEA DEVIL: We shall destroy man and reclaim the planet.
DOCTOR: You may win a few victories to begin with but eventually you're bound to lose.
SEA DEVIL: There are many thousands of our people in hibernation in this base. We have other colonies hidden all round the world. We shall be the victors in the war between the land and the sea.
DOCTOR: There's no need for a war. Why can't you share the planet?
SEA DEVIL: That would be impossible.
DOCTOR: The depths of the sea and those areas on Earth where man cannot live can be yours.
SEA DEVIL: And man would agree to that?
DOCTOR: There's a chance. Wouldn't it be better to try for a peace, than to launch yourself into a war that you cannot possibly win? Let me return to the humans, and I will endeavour to make a peace for you.
SEA DEVIL: Perhaps it would be possible.
MASTER: No! The Doctor is your deadly enemy! He must be destroyed!

[Hart's office]

(Walker sits at Hart's desk, stirring his tea.)
WALKER: Captain Hart, there's only one way to deal with this problem. You have to attack.
HART: You're throwing away the lives of the men in that submarine, sir!
WALKER: Ugh. Oh, pass me the sugar, my dear, will you?
(Jo obliges.)
HART: There's a chance that some of the crew may still be alive.
JO: And what about the Doctor? He may still be alive down there too!
HART: Yes.
WALKER: Well, this is war, my dear, and war calls for sacrifice. Any chance of any more toast, my dear?
BLYTHE: Yes, sir.
(Blythe takes the toast rack and leaves.)
WALKER: The order's already been given. Ships are converging on this area from ports all over England. Our line is quite clear. Immediate retaliation with everything we've got.
JO: Look, do you realise that that's murder?
WALKER: Murder? War always is, my dear. Where on Earth's that girl with my toast?

[Flag ship]

(The task force prepares for battle, readying torpedoes and gun batteries.)
ADMIRAL: Inform Ministry of Defence. Task Force now in position and ready to attack.
CPO: Aye, aye, sir.

[Naval base radio room]

BOWMAN: Roger Task Force. Over and out.
WALKER: What is it?
HART: The Task Force is in position, sir.
WALKER: Excellent! Cry havoc and let slip the dogs of war.

[Sea Devils base]

DOCTOR: I beg you not to listen to this man. He's the personification of evil.
SEA DEVIL: The Master is our friend.
DOCTOR: He wants only to provoke a war.
MASTER: I do not! I came here to help you revive your people.
DOCTOR: Why should you need his help?
SEA DEVIL: Our hibernation unit is faulty.
MASTER: And I can now repair it for you.
DOCTOR: But why revive your people only to have them killed? Let me try and negotiate that peace for you.
MASTER: The last time this man encountered your race, he tricked them. The humans destroyed them all.
SEA DEVIL: Is that true?
DOCTOR: Yes. I tried to make peace but I failed.
MASTER: You see? He admits it. Man is weak. Your conquest will be easy.
DOCTOR: Believe me, man is not weak. He's only too proficient at devising weapons of annihilation and using them.

[Hart's office]

WALKER: Tell them to carry out their orders.
JO: No! Look, please, you've got to do something! Can't you stop him?
HART: I wish you'd reconsider, sir.
WALKER: Captain Hart, I have full authority. Now, are you going to carry out my order or must I replace you with someone who will?

[Sea Devils base]

SEA DEVIL: He says man is weak. You said man is strong.
MASTER: He's lying! He's trying to frighten you!
SEA DEVIL: No. I do not think he lies. Perhaps it would be better to make peace.
MASTER: Don't trust him!
(The Doctor raises his right hand and the sea devil puts its own hand against it.)

[Hart's office]

HART: I'm sorry, Jo.

[Sea Devils base]

SEA DEVIL: You will negotiate a truce between my people and the humans.

[Flag ship]

ADMIRAL: Commence attack.
SAILOR: Urgent attack.
(Depth charges are fired.)

[Sea Devils base]

MASTER: You are throwing away the control of this planet! The humans will never make peace with you!
(Boom! as a depth charge finds its target and sends everyone staggering. The barrage continues, knocking them to the floor.)
MASTER: Is this the promised peace? Can't you see that the humans are determined to wipe you out?
SEA DEVIL: You are right! These apes cannot be trusted! Take him away and kill him!
(The Doctor is taken away down a dark passage as the barrage continues. He manages to get free of his escort just before a section of roof comes down on them. He goes back to one of the crushed reptiles, brushes off the sand and rock, and takes its weapon.)
SEA DEVIL: Destroy the ships! We must retaliate.
MASTER: Not yet. If I am to revive your people, I need time.
SEA DEVIL: What would you have us do?
MASTER: Convince the humans that their attack has been a success.

[Flag ship]

(A Lieutenant Commander is scanning the attack area.)
OFFICER: Sir?
(The Admiral takes a look, and sees two dead reptiles floating in the water.)
ADMIRAL: Cease fire.

[Sea Devils base]

(A wall monitor shows the position of four surface vessels.)
MASTER: You see? My plan has worked.
SEA DEVIL: We could still destroy their ships before they are out of range.
MASTER: No, let them go. Let them think that they have won.
(The Master and the chief reptile touch hands, or glove.)
SEA DEVIL: You will now revive the rest of my people.
MASTER: Yes, but first the trigger mechanism on your reactivation unit is faulty. I need electronic equipment to build a new one.
SEA DEVIL: And where will you obtain this?
MASTER: The humans will provide it. We shall attack their base.

[Sea Devils base - detention area]

(The Doctor enters a section containing a reptile lying on the floor and some electronic equipment, and a survival suit from the submarine. In an adjoining cell, the submarine's First Officer is trying to force open a door with a small porthole in it using just a small knife.)
RIDGEWAY: Optimistic, Number One, but I admire your pluck. Here, let me.
MITCHELL: Would you like to try, sir?
(The Doctor appears in the port hole.)
DOCTOR: Good afternoon, gentlemen. Er, look, would you mind keeping back for a moment? That is if you want to get out? Thank you!
(The Doctor uses the sea devil weapon to blast open the door.)
RIDGEWAY: Who the blazes are you?
DOCTOR: Look, I've no time to explain now. Where are the rest of your men?
RIDGEWAY: Still in the submarine.
DOCTOR: Is the submarine still operational?
RIDGEWAY: Should be.
MITCHELL: They've ripped out the communicators and the escape gear, as you can see.
RIDGEWAY: But left the engines alone.
MITCHELL: Yes.
DOCTOR: Where's the sub now?
RIDGEWAY: In a kind of undersea harbour.
DOCTOR: Can you find the way?
RIDGEWAY: I think so, yes.
DOCTOR: Right, you'd better lead on. Here, take this. It's a gun. Now come on, let's hurry.

[Submarine]

(Ridgeway, with the weapon, and the Doctor come down the ladder to find a reptile.)
DOCTOR: No, no! Don't kill him!
(Ridgeway fires anyway.)
DOCTOR: There's no need to have done that!
RIDGEWAY: Any more of them, Summers?
SUMMERS: Yes, there's some more on guard up top, sir.
RIDGEWAY: We've dealt with them already. Right, action stations! We're getting under way.
(Ridgeway tosses the weapon over his shoulder to Mitchell.)
MITCHELL: Aye, aye, sir.

[Sea Devils base]

SEA DEVIL: The humans have escaped.
MASTER: The submarine! They've recaptured it.

[Submarine]

(The submarine is part way out of a rock face cave when the bright forcefield comes on.)
MITCHELL: Maximum revs, sir.
DOCTOR: They're holding us back with some kind of forcefield.

[Sea Devils base]

(The monitor shows the submarine being pushed back through the rock face.)
SEA DEVIL: They cannot escape us now.

[Submarine]

DOCTOR: Well, you could try firing your torpedoes at the cave wall and blasting yourselves free.
MITCHELL: We're still halfway in the cave, sir. We could blow ourselves up.
DOCTOR: That's a risk you'll have to take.
RIDGEWAY: Forward ends, this is the Captain. Load all bow tubes. Open one and two bow caps.
RATING [OC]: All bow heads open. Ready to fire, sir.
DOCTOR: Well, come on, then. You've got to risk it. RIDGEWAY: Stand by bow salvo.
RATING [OC]: Standing by, sir.
RIDGEWAY: Fire one. Fire two.
(Boom! and the submarine shoots backwards out of the cave.)
RIDGEWAY: Any damage forward, Chief?
SUMMERS: No damage to tell, sir.
RIDGEWAY: Thank you. All right, stand by to surface, Number One. MITCHELL: Aye, aye, sir.
RIDGEWAY: We're going home.

[Sea Devils base]

(The monitor shows the submarine making good speed.)
SEA DEVIL: They can tell the humans how to find our base.
MASTER: It's of no importance. Before they can attack us, we shall attack them.

[Hart's office]

JO: Doctor! I thought you were dead!
DOCTOR: Dead? No, I don't think so.
JO: When I saw that thing come up empty, I thought I'd never see you again.
WALKER: Well, well, well, so the heroes have returned.
DOCTOR: Captain Hart, what idiot ordered an all-out attack just as I was on the verge of finding a peaceful solution?
JO: But it wasn't Captain Hart's fault. It was this...
HART: I'm terribly sorry. This is Mister Walker. He's the Parliamentary Private Secretary in charge of this business.
WALKER: I'm the idiot you've just been talking about. Absolutely splendid lunch, old man.
DOCTOR: You ordered the attack?
WALKER: I did.
DOCTOR: Did you give any thought at all, sir, as to what you were doing?
WALKER: Our duty is to destroy the Queen's enemies. Don't you know your national anthem? Confound their politics, frustrate their knavish tricks.
DOCTOR: That, sir, is an extremely insular point of view. At the precise moment of the attack, I was negotiating a peace.
WALKER: Peace? Huh. What, when they've been attacking our shipping and heaven alone knows what? I think you've got it all wrong, old man. Seek and destroy. That's what you chaps say, isn't it?
DOCTOR: But the point, Mister Parliamentary Private Secretary, is that you have not destroyed. You have just made them angry. Very, very angry!
(So angry that a reptile has just taken out the lone sentry on the beach.)
WALKER: I'm going to get on to the Minister, and I'm going to ask him to seek approval for an immediate attack with nuclear weapons.
DOCTOR: But that, sir, would be tantamount to murder.
WALKER: Oh, come, come, Doctor. You speak as if these creatures are human. We're not going to hand over the world to a lot of lizards, you know.
DOCTOR: You can share it with them, surely?
WALKER: Oh, come. Really, Doctor.
DOCTOR: Look, let me make one final attempt to negotiate.
WALKER: Well, you didn't get very far last time, did you?
DOCTOR: Wouldn't you like to be the man behind a peaceful settlement? Walker the peacemaker, they'd call you. Or would you prefer to be known as the man responsible for launching a full-scale war!
WALKER: You can actually communicate with these creatures?
DOCTOR: Yes.
WALKER: And you'd be willing to undertake the preliminary negotiations yourself?
DOCTOR: Just leave it to me.
JO: Doctor, you're not thinking of going down there again?
DOCTOR: Jo, it's the only way.
JO: But, Doctor, it's far too dangerous!
DOCTOR: Don't you understand, Jo? I've got to go down there of my own free will as a gesture of good faith.

[Naval base]

(More reptiles are coming ashore and making their way into the base.)
HART: Doctor, do you think you're doing the right thing?
DOCTOR: I'm doing the only thing possible, Captain Hart, if we're to avoid a major conflict.
HART: Suppose they won't listen to you?
JO: Doctor!
(A reptile raises its weapon at them. Without hesitation, the Doctor runs to the reptile, knocks the weapon out of its hand and slams its head against a nearby wall. A second reptile gets a double-handed punch to the midsection then jaw.)
DOCTOR: All right, Captain Hart, get these two out of here.
JO: Doctor, look out!
(Another reptile grabs the Doctor's neck from behind and puts pressure on. He blacks out. More reptiles arrive and raise their weapons.)
MASTER: No! No. Take them inside.
(Hart and Jo half-carry the Doctor back to the main building.)
MASTER: Dear, oh dear, Doctor. Will you never learn?
(All over the base, naval personnel are being rounded up and shut in building 289.)

[Outside Hart's office]

MASTER: Now, Doctor, for your information the capture of this naval base is the first step in the return of this planet to its rightful owners. Right, bring him in, will you?

[Hart's office]

DOCTOR: How do you hope to achieve that?
MASTER: As you know, our friends here have underground and underwater bases all over the world. Well, I propose to reactivate them.
DOCTOR: You haven't reactivated them yet, have you?
MASTER: Er, not yet, no. But I can, with your help.
DOCTOR: I wondered why I was still alive.
MASTER: I advise you not to give me any trouble, Doctor. Not if you value the life of every man on this base.

[Naval base radio room]

(Hart tries the radio.)
HART: It's no good! They've cut the power supply!
JO: Shush! Look, there's still some of them in there.
WALKER: This is monstrous! What are you going to do about it, Captain Hart?
JO: Captain Hart, what about this?
(Jo points at a hatch in the ceiling.)
HART: Yes, we should be able to open it. But I could never get through the ventilation shaft up there.
JO: No, but I could.

[Naval base stores]

(The Master gets their reptile escort to wait outside.)
MASTER: Now then, Doctor, my problem is this. During millions of years of hibernation, the reactivation machinery has deteriorated. I now find it necessary to build a trigger mechanism for it.
DOCTOR: And how do you hope to do that?
MASTER: With your cooperation. All the equipment we need is here.

[Naval base radio room]

(Hart is unscrewing the ceiling hatch.)
WALKER: This could have the most dreadful consequences! Supposing you get caught? They might take reprisals against the innocent!
(Jo climbs onto the table.)
HART: Come on, Jo. Now, once you're through the shaft, there's a hatch that comes out onto the roof of this building.
JO: Okay.
HART: Are you ready? Hup.
(Hart lifts Jo into the shaft.)
HART: That's it.
WALKER: Don't you think we ought to leave these things to the Doctor? He's, er, he's not going to try and trick them, is he? (Jo drags herself along on her stomach to the grill on the roof.)

[Naval Base stores]

MASTER: I've drawn up some preliminary plans here. There.
DOCTOR: Good grief!
MASTER: Why? What is the matter?
DOCTOR: Well, this circuit here, it's completely misplaced. And also you'll need far more power through to your main dipode.
MASTER: And you think you can correct this fault?
DOCTOR: Yes, I think so. Let's see.
(Jo climbs down from the roof and goes through the base.)
(A reptile enters the stores.)
MASTER: Well, Doctor?
DOCTOR: How about a little test? Right, here goes.
(The Doctor switches it on and the reptile clutches its head in agony.)

[Hart's office]

(So does the one in Hart's office so Jo runs through and opens the radio room door to release Hart and Walker.)
HART: What the blazes?
JO: The Doctor's doing it. Now come on, quickly, please.
(Walker can't bring himself to push past the suffering reptile, and goes back into the radio room.)

[Naval base]

(Hart and Jo leave the main building, past two more writhing reptiles. They come across a fallen Marine and Hart takes his rifle.)
HART: We must find the hovercraft pilot.
JO: It's all right. I can fly one. Come on!
(A hovercraft - SRN5 - is sitting on the shingle. Hart shoots at a group of approaching reptiles while Jo gets into the pilot's seat and starts it up. He manages to kill them before the hovercraft's skirts inflate and they glide down onto the sea.)

[Naval base stores]

MASTER: Switch the power off!
(The Master pulls the plug out of the wall and the reptile stands still.)
MASTER: What happened?
DOCTOR: I must have had the frequency too high. I'm sorry about that. Ah, no, I see what it is. I had the output jack in the input socket. There. Yeah, there that should work all right now.
MASTER: We shan't know for sure till we get it back to their base and build it into their power system.
DOCTOR: We?
MASTER: Yes, Doctor. You're coming with me.
DOCTOR: Oh, I see.
(The reptile leader is escorted in.)
SEA DEVIL: This noise, what has been happening?
MASTER: Teething troubles, that's all.
SEA DEVIL: Is the work completed?
MASTER: Yes, I've now finished.
SEA DEVIL: Then we shall return to our base.
MASTER: Well, Doctor? Shall we go?

[Naval base]

(The hovercraft returns to the beach and marines come out.)
SEA DEVIL: Guard them. I must alert the others.
(The Master and the Doctor are locked back in the stores. Hart leads the troop of marines onto the beach and the battle for the base begins. Despite the difference in weaponry, the marines have the upper hand and are cutting down reptiles far more quickly than they take casualties of their own. Jo emerges last.)

[Naval base stores]

DOCTOR: Well, it seems as if things aren't quite going according to plan.
MASTER: Look, we must break out of here! I've got to get this device down to your base.
OFFICER [OC]: Myers, check that storeroom!
(The reptile puts the Master behind him as the door opens and a Petty Officer looks in.)
MYERS: Looks all right.
DOCTOR: Look out behind you!
(Myers puts five rounds rapid into the reptile.)
DOCTOR: This man is an extremely dangerous criminal, so guard him well. Now, have you seen Captain Hart and Miss Grant?
MYERS: I'm not sure, sir.
DOCTOR: Right, I'd better go and find them.
MYERS: Right, I'll stay with this bloke.
DOCTOR: Yeah, do that. And watch him!
(The Doctor leaves. Myers keeps his rifle leveled at the Master.)
MASTER: There's been a misunderstanding here, you know. I'm not the man that you want. There's been a mistake.
(Myers gets treated to a full Look.)
MASTER: Understand? A mistake.
(The Master pushes the rifle barrel aside.)

[Naval base]

(Hart and a rating load a two inch gun emplacement and use it against a troop of reptiles. The Doctor arrives.)
DOCTOR: Seen Jo Grant anywhere?
HART: She's on the beach.
(The Doctor sees the Master run through the gate onto the beach, carrying the trigger mechanism.)

[Beach and sea]

(There are a pair of bright orange one-man jet boats just above the surf line. The Master puts the mechanism in one and launches it. The Doctor runs down the beach to the second and launches that, giving chase. The reptile leader and his surviving warriors run into the sea. The Master beaches his craft on another sandy beach and the Doctor catches up to him.)
MASTER: I'm sorry, Doctor.
(The Master points to a reptile diving bell, then six reptiles come over the dunes.)

[Sea Devils base]

(The Master and the Doctor are attaching the trigger mechanism to the reptile's hibernation equipment.)
SEA DEVIL: Many of my people have been killed.
MASTER: It was a necessary sacrifice.
SEA DEVIL: You said man was weak.
MASTER: And so he is. Soon you can surge from the seas in your millions and exterminate him.
DOCTOR: Don't listen to him. Why begin a long and bloody war where thousands will be killed on both sides?
SEA DEVIL: We shall destroy man and reclaim the planet.
DOCTOR: Is there nothing I can say to make you reconsider?
SEA DEVIL: Nothing.
DOCTOR: I'm sorry.
SEA DEVIL: Is the machine ready?
MASTER: It is.
(The Doctor adjusts a lever on the top.)
SEA DEVIL: Then activate it.
MASTER: Allow me, Doctor. We don't want any accidents this time.
DOCTOR: The power may take some time to build up, you know.
(The Master switches the trigger mechanism on.)
MASTER: I suggest you now dispose of this man.
SEA DEVIL: Take them both to the cages.
MASTER: What's the meaning of this? I'm your ally!
SEA DEVIL: Take them!
MASTER: I helped you! I helped you!
(An armada of surface vessels and submarines are approaching the Solent.)

[Hart's office]

WALKER: Now, perhaps you'll admit I was right all along. Massive nuclear strike ,it's the only way.
JO: But not until we know what's happened to the Doctor.
BLYTHE: Excuse me, sir. I've just seen Lieutenant Scott. He said he saw the Doctor heading out to sea.
WALKER: Ha, ha. Gone to join his friends. Gone over to the other side.
BLYTHE: He seemed to be chasing another boat.
JO: He must have been after the Master.
WALKER: Well, be that as it may, they'll both have to take their chances. I'm going to put an end to these creatures right away. Kindly get me the Minister on the phone. I'm going to request that we launch a nuclear strike. Now.

[Sea Devils base]

MASTER: Look, I demand you take me back to your chief! Immediately!
DOCTOR: You seem to be losing your touch.

[Sea Devils base - cell]

MASTER: Once they see that the device works properly, they'll release me.
DOCTOR: I very much doubt it. You see, before you reactivated it, I reversed the polarity of the neutron flow.
MASTER: You did what? You realise what will happen?
DOCTOR: Oh, yes. Do you?
MASTER: Well, there'll be a massive reverse feedback into their whole power system.
DOCTOR: Exactly. In about ten minutes from now the whole place should go up. Enjoy your revenge.
(The Master goes to the small porthole and shouts out.)
MASTER: Guards! Guards, come back! You must release me! I must talk to your chief! Let me out! We're all in danger! Let me out!
DOCTOR: You're wasting your time, you know. Even if they heard you, they couldn't do anything about it.
MASTER: Why?
DOCTOR: Well, I built a self-destruct mechanism into the main control switch. You can't turn it off.
MASTER: But but we'll both be killed.
DOCTOR: That's right. Unless we can both escape.

[Naval base radio room]

BOWMAN: Ships moving into position now, sir.
WALKER: Very well. This time we'll continue the attack until those creatures are finally destroyed.

[Sea Devils base - cell]

(The Doctor uses his sonic screwdriver to unlock the cell.)
DOCTOR: You see? Come on.

[Sea Devils base - detention area]

DOCTOR: Submarine escape equipment. Now, all we've got to do is find the airlock.
MASTER: Airlock?
DOCTOR: Yes, there must be one around here somewhere. Otherwise how else did we get down in those capsules? Here you are. Put this on.

[Naval base radio room]

HART: Won't be long now.
JO: Suppose the Doctor manages to escape from that place?
HART: Not much chance, I'm afraid.
JO: Yes, but just suppose?
HART: Get a high-speed hovercraft over that area. I want a complete sweep before the attack.
BOWMAN: Aye, aye, sir.
(Two figures in orange survival suits are bobbing up and down in the sea, waving. The crew of hovercraft XT492 pull the Master aboard, then it is the Doctor's turn. Safely inside the hovercraft, the Master clutches his chest and falls to the floor.)

[Sea Devils base]

(The power in the trigger mechanism builds towards maximum.)
SEA DEVIL: This device is causing the power to overload.
(He switches it off, and there is a little bang. Then something under the sea goes KaBOOM several times.)

[Naval base radio room]

BOWMAN: Large underwater explosion reported, sir.
WALKER: What? Has the attack started already?
BOWMAN: No, sir, before the attack. And they've picked up two survivors. One of them was in a bad way. They've radioed for an ambulance to stand by.
JO: Did they... did they say who?
BOWMAN: No, Miss.

[Beach]

(SRN5 lands as Jo and a pair of stretcher bearers run down the shingle. The Doctor goes to meet Jo and Hart.)
JO: They said someone was hurt?
DOCTOR: It's the Master. He collapsed soon after they picked us up.
HART: Well then, Doctor, what happened?
DOCTOR: I managed to destroy their base for you.
HART: Thank goodness. Well done.
DOCTOR: Well, I did what I had to to prevent a war.
(The stretcher party come back with the Master.)
JO: He's dead.
MEDIC: We were too late. The doctor in the hovercraft said so.
DOCTOR: Doctor? What doctor?
(The Doctor removes a latex mask from the man on the stretcher.)
SAILOR: I must obey. I must obey. I must obey. I must obey. I must obey. I must obey.
(The Master flies the hovercraft back out to sea.)
SAILOR: I must obey. I must obey.