PIERCE [OC]: Let's go, people. Welcome to Blackport. We don't have much time, but we've appointed the best naval training personnel to prep us for the descent. They'll be doing everything they can to prime us, both physically and mentally, monitor our stamina, heart rate and blood pressure, and help get us used to the water.

[Briefing room]

PIERCE: We'll be descending to the rendezvous point in this submersible, to a depth of 8,000 metres, five miles down. Our journey will take 2 hours and 17 minutes. The submersible is currently on a launch vessel with warship escorts, bound for the descent point. On the dive will be the Ambassador, myself, Captain Mackie for communication, Ms Tso for science and technology, and our two diplomatic representatives, Mister Singh...
SINGH: Oh. Ravi.
PIERCE: ..and Mister Campbell.
CAMPBELL: Ted. It's a pleasure.
BARCLAY: Have we ever been this deep before?
MIN TSO: Smaller missions of one or two people. Nothing of this scale.
SINGH: And I bet they were trained specialists with years of experience. We have days to prepare for this.
PIERCE: Yeah, of course there's a risk. What we're doing today is unprecedented, but this is the toughest submersible on the planet.

[Control room]

KATE: This is Kate Lethbridge-Stewart to launch vessel. Captain Gaitz, how are we doing?

[RRS James Cook Bridge]

GAITZ: Just finishing final checks.
(Submersible getting hooked up to the crane.)

[Control room]

GAITZ [OC]: Pre-launch checks complete. Submersible ready for deployment.

[Hotel suite]

BARBARA: Things go wrong all the time. What if it springs a leak? That kind of pressure, you'll be crushed to death, pulverised in an instant.
BARCLAY: Oh, just keep your voice down, will you?
BARBARA: If you do this, you might never come back.
TV: Deep sea pressure compresses air-filled spaces in the body, leading to lung compression and potential collapse...

[Briefing room]

PIERCE: Now, once we arrive at the descent point, Homo Aqua will transfer us to their environment.
BARCLAY: Well, what about the descent? Are they helping us with that?
PIERCE: For the descent, we're on our own.
CAMPBELL: We're not alone. We're never alone.
BARCLAY: Sorry?
CAMPBELL: We're a team.
BARCLAY: Okay.
CAMPBELL: Yeah.

[Swimming pool]

(Barclay is sitting on the side of the pool.)
PIERCE: Transfer by helicopter is at 0600. Indemnity forms need signing, and legal have noted you haven't replied to their emails. You do need to make sure your will is up to date.
(Barclay falls gently into the water.)

[Hotel suite]

TV: What he lacks in experience and expertise, Dupont appeared to make up for in passion. His unconventional communication style in such crucial peace negotiations...
BARCLAY: So, this is it, then.
TV: ..seems to have convinced the Aquakind Ambassador...
BARCLAY: Do I get a hug before I go?
TV: ..but questions remain...
BARBARA: It might take weeks to clean the roads. The city's been shut down. You can't go anywhere.
BARCLAY: Yeah, well, it's lucky you're back here, then, isn't it?
KIRBY: We're at war.
BARCLAY: I know. I'm going to sort it.
KIRBY: How? How are you going to sort anything? Do you know what they're calling you on TikTok?
BARCLAY: Oh, I don't really care...
KIRBY: They're saying you're useless. Traitor. Boot-licker. Bleeding-heart puppet, too thick to negotiate.
BARBARA: That's not fair!
KIRBY: It doesn't matter, cos either way we're screwed! Either... either they kill us or we kill ourselves! I hate the lot of you!
(Storms out.)
BARBARA: They're worried sick about you.
BARCLAY: Yeah, I know. I'm sorry, but I promise you, I'm going to be fine. No, no, no, no, no, please, please. Please, don't. I've got this, okay? I can do this. I mean, for God's sake, I nursed Mum through cancer, didn't I? Didn't I? Bloody hell, if I can get through that, oh, I can get through anything, can't I? I've got to be strong for everyone else, right? Cos everyone's counting on me. Kate, Salt and Kirby... the whole world!
BARBARA: You don't have to be strong for me.
BARCLAY: Barbara... Barbara, I'm so scared!
KIRBY: I'm sorry, Dad.
BARCLAY: Right, that's it. Okay, now. You all right? Yeah?
KIRBY: Yeah, sorry.

[Chinook helicopter]

CAMPBELL: Ravi?
SINGH: Hmm?
CAMPBELL: Are you okay?
SINGH: Mmm mmm. I've been a diplomat for three months. Three months! I'm... I'm not cut out for this.
BARCLAY: Of course you are. You're going to come back a hero. You know that, right?
CAMPBELL: This'll set us up for life. Speaking tours, book deals, the works.
SINGH: Do you think I'll get a girlfriend out of it?
BARCLAY: They're going to be queuing up, mate.
CAMPBELL: All you've got to do is hang in there. You know, sometimes I can hear my life coach. "Hold the line, Ted." That's what he'd say in moments like these, moments of fear, of self-doubt. "Believe in yourself, trust in fate and hold the line." Guy got struck by lightning. Dead at 50.
SINGH: Seriously?
(Campbell laughs.)
BARCLAY: What's in the box?
CAMPBELL: Diplomatic gift... from all nations.
MACKIE: And what are Homo Aqua supposed to do with a globe?
CAMPBELL: :They see the world from underneath, right? From the depths. Never like this.
MACKIE: Where are they going to put it, Ted?
CAMPBELL: Who knows? Maybe they've got, like, coral mantlepieces.
SINGH: Aren't you fazed by any of this?
CAMPBELL: We're going to be fine. Wood floats.

[RRS James Cook Launch deck]

PIERCE: In the words of a great man, "We can be heroes." Let's save the world.
(Pierce leads the way into submersible XR5.)

[RRS James Cook Bridge]

GAITZ: Seal the hatch. Control to all units. We are clear.
(The submariners are sealed in with hefty bolts.)
HARPER: Confirm lock.

[Control room]

KATE: Captain Gaitz, handing control over to you.

[RRS James Cook Bridge]

GAITZ: Okay, let's pick it up. Let's move it out.

[Submersible]

GAITZ [OC]: Taking you off the ship now. Good luck, everybody.
KATE [OC]: Good luck to you all.

[RRS James Cook]

CREWMAN: Vessel looking stable, sir. Over.
HARPER: Deployment is go.
GAITZ [OC]: Control to deck. All readings are stable. We are good to go. Over.

[Submersible]

BARCLAY: Are you okay, Ted?
CAMPBELL: Oh, yeah, terrific. Yep.

[RSS James Cook Bridge]

GAITZ: Gently...

[Submersible]

GAITZ [OC]: Prepare for release.
PIERCE: This is it.
SINGH: Mmm.

[RSS James Cook bridge]

GAITZ: On my mark.
HARPER: In three, two, one.
GAITZ: Mark.

[Submersible]

(XR5 is dropped into the water.)
PIERCE: And we're off.
(The cable tether plays out as they descend.)
SINGH: How long's it been?
MACKIE: Seven minutes.
SINGH: Oh...
CAMPBELL: Gone dark already. No sunlight. Imagine living like this all the time. Anyway, we're fine, aren't we? Can I get a "Yes, Ted"?
BARCLAY: Yes, Ted.
CAMPBELL: I've got some team-bonding word games if anyone's interested.
PIERCE: No, thank you.
MACKIE: How did you end up here anyway?
SINGH: Oh... There was a diplomatic lottery for the two last seats and... India won. Or lost, depending on how you see it. There was rumours flying around that the draw was rigged, that most people had their names removed cos they didn't want to go.
BARCLAY: I mean, one way to look at it is we're pioneers, like those early astronauts. You know, where would we be if they hadn't taken that "one giant leap"?
CAMPBELL: What the hell is that?
PIERCE: It's adjusting to the pressure.
CAMPBELL: Are you sure?
BARCLAY: It's okay, Ted. Just breathe.
CAMPBELL: Oh, I'm... I'm breathing. I'm... I'm fine.
MACKIE: What do you think we'll get for dinner when we're back on the ship tonight, hmm? Think they'll spoil us?
MIN TSO: They bloody should!
BARCLAY: No, it'll just be canteen sandwiches again.
MACKIE: It's tough being a hero!
CAMPBELL: Is this... is this water? This... this is water. There is water in here!
PIERCE: Ted...
CAMPBELL: Radio the ship!
BARCLAY: Ted, calm down. It's condensation.
CAMPBELL: How the hell do you know?
BARCLAY: Because I read page six of the safety briefing!
CAMPBELL: Yeah. Sorry. I...
SINGH: I guess if there was a breach, this thing would implode before we knew about it, so...
PIERCE: Can everyone just shut up now, please?

[Cabinet Office Briefing Room A - Downing Street]

LAKHANI: The economy's already tanking. If we start closing shipping lanes, the effect could be catastrophic.
KATE: Hello.
ASSISTANT: Sorry, sir. Kate Lethbridge-Stewart.
SHAW: Okay.
KATE: It is a directive of the United Nations that UNIT have a voice in any emergency discussions.
SHAW: Sorry, we started a little early. A lot of people couldn't make it. Some of the Cabinet are joining remotely.
KATE: With respect, it's a phone call. I'll catch up. Please, carry on.
GUNSBERG: The United States relies on maritime trade and we will defend ourselves vigorously against any disruption to our networks. The US military is arming itself with sonic weaponry. Sound cannons are used for crowd control, but we've adapted the technology for underwater use.
DUSSOLIER: We've identified key shipping lanes we need to protect. The English Channel, the Panama Canal, the Suez.
GUNSBERG: Ultra-high frequency blasts could disable or confuse Homo Aqua, paving the way for traditional weapons... if required.
KATE: Sorry, why are we discussing weapons? Our focus is on diplomacy. And there is an armistice agreement in place now to stop further violence.
GUNSBERG: Someone's got to be the first to break it.
KATE: Sir, our focus should be on diplomacy. That's why six of our diplomats are risking their lives today.
DUSSOLIER: They're buying time, that's all they're doing. It's song and dance, smoke and mirrors.
SHAW: The General's right. We make decisions, here, in this room. The Western Front, the Falklands, Iraq. Wars are fought and won at this table. They think they own the water, but while they were splish-splashing around 300 million years ago, we crawled out of the water... then we conquered it.
SPIERS: We built a civilisation that depends on our oceans to power our homes, feed our crops and keep us alive.
KATE: And keep you in business.
LAKHANI: Sorry, but I agree with Kate. Their civilisation is so ancient and so powerful, aren't they a gift? Couldn't they help solve not just the climate crisis but so much more, if we had them onside?
GUNSBERG: We're never going to get them onside. They want us gone.
LAKHANI: If they wanted us gone, I think that would've already happened.
SPIERS: If they were gone, we could have access to their technology. Think of it. Treasure from the ocean floor.
KATE: This is a diplomatic crisis, not a pirate raid.
LAKHANI: That's what the West does best. Colonise and plunder.
SPIERS: I'm sorry, but I'm 60 percent water.
DUSSOLIER: We all are.
SHAW: Don't tell me we don't own the water. If Homo Aqua want a war between the land and the sea, we'll take the sea.
KATE: Sir, this kind of rhetoric is irresponsible.
SPIERS: If you're trying to keep the peace, you've already failed.
DUSSOLIER: If you're not onside, we might have to reconsider our options. Diplomatic responsibility can easily be transferred.
KATE: What, to you?
SPIERS: A global emergency committee could guide Homo Aqua through a peace process that puts mankind first...
KATE: Sorry...
SPIERS: ..not UNIT.
KATE: ..but what is Sir Keith doing in an emergency meeting? He's not Cabinet or Agency, and his companies, at this very moment, are still pumping millions of litres of sewage into our waterways.
DUSSOLIER: These processes take time.
KATE: And don't get me started on General Dussolier, who leaked confidential information to the press.
SPIERS: I think you need to calm down, love.
KATE: This is a national security matter.
SHAW: The fact is we need industry and our allies onside. We can't do this alone.

[Submersible]

SINGH: What's going to happen down there?
BARCLAY: Ravi, come on. We've already said, we don't know.
SINGH: So, what if this is a trick and they want hostages?
PIERCE: We didn't take any hostages, why should they?
SINGH: Cos that's what happens in war.
BARCLAY: Look, I promise you, we're going to sort this, okay? I don't know how we will, but we will, cos my kid is not living through a war.
MACKIE: I never had kids, but if I get out of here, I'm going to call my brother. We haven't spoken for 20 years.
BARCLAY: Good for you.
SINGH: First thing I'm doing is taking my family out for a meal. All 19 of us.
MACKIE: Nineteen!
SINGH: Yeah. Yeah, and I'm paying.
CAMPBELL: Oh, it's so hot. This suit... How deep are we?
BARCLAY: All right, Ted, come on. Come on, Ted, don't think about that.
CAMPBELL: I watched this show where they made a human out of pig parts - bones and meat - and they put it in a diving suit, and... and they... ..they tested it for deep-sea pressure, and it...
PIERCE: Mister Campbell!
CAMPBELL: ..and it just turned to soup in a split second.
BARCLAY: Okay, Ted. Ted, no one wants to hear this.
CAMPBELL: And I don't want to be soup!
BARCLAY: All right, okay. It's okay, you're okay. Ted, come on! Come on! Look at me. Just breathe. Just breathe now. Breathe now, please, with me, okay? Slow and steady, with me. Cos we're a team, aren't we? Yeah? Okay. Okay?
CAMPBELL: Thank you.

[Cabinet Office Briefing Room A - Downing Street]

TV: Well, all six delegates should now be descending to the ocean floor. Meanwhile, emergency crews continue to clear arterial roads through major cities...
SHAW: Can you turn that off, please?
TV: ..while the national curfew remains in place for at least twelve...
SPIERS: A few days ago, the situation was dire. We were staring down the barrel of unprecedented financial and energy crises. Now it's catastrophic.
GUNSBERG: We cannot surrender control of this planet. Look what they did to us in 15 minutes. If they wanted to, they could wipe us out.
DUSSOLIER: UNIT are looking after their own interests. It is our moral duty to stop Aquakind, however we can.
SPIERS: Harry, I know you have a lot on your plate right now.
SHAW: Alison has tests today. I should be with her.
SPIERS: I already know you value my opinion. And maybe my money. The Generals have decades of military strategy under their belts. Let us guide you, take the pressure off.
SHAW: When I became Prime Minister, I made a promise to my grandchildren to leave this country better than I found it.
GUNSBERG: Sir, if we don't win this war - and war is what it is... ..there will be no grandchildren.
SPIERS: But we believe there is a way through this. A new stratagem, just between us. We're calling it Severance.

[Control room]

IBRAHIM: I found some instant coffee. And... biscuits.
KATE: I won't ask you what you had to do for those.
IBRAHIM: Ha! Yeah, best not. They'll be okay. But you look exhausted.
KATE: Well, I've had six hours' sleep in three days. This morning, I showered in a sink, sent good people five miles under the ocean, then sat through a COBRA meeting with a room full of warmongers.
IBRAHIM: You need a break.
KATE: They want to shut UNIT out. And if we lose control, who steps in? Who decides the future of the human race?
SHIRLEY: Sorry, the submersible's entering the deepest part of the trench.
KATE: Yeah. Get me Captain Gaitz, I want a situation report ASAP.
SHIRLEY: This is uncharted territory. They're off the maps now.
KATE: This'll be the longest night of our lives.

[Submersible]

SINGH: What's that? What's happened?
MIN TSO: I think we've stopped.
BARCLAY: Are we... are we on the seabed?
PIERCE: Negative. This is SU-1 to surface. Surface, this is SU-1. Hello? Is anyone there?
SINGH: Oh, my God...
PIERCE: We're moving again.

[Control room]

KATE: Captain, what's happening?

[Submersible]

MIN TSO: We're moving at 12 knots. 18 knots.

[Control room]

SHIRLEY: These readings don't make sense.

[Submersible]

MACKIE: That's not possible!
MIN TSO: 30 knots! Something's taken control!

[RSS James Cook Bridge]

HARPER: How are they moving so fast? Captain!

[Control room]

KATE: What...? Are they being dragged?
SHIRLEY: Mmm, think so. They're descending twice as fast. Steve, how's the pressure?
CHESNEY: Pressure is holding.

[RSS James Cook Bridge]

GAITZ: We've lost comms. Ping the transponder!
HARPER: No response.

[Submersible]

BARCLAY: Okay, do you feel that? Do you feel like we're descending again?
CAMPBELL: Why is there no radio contact?
PIERCE: I don't know.
MIN TSO: Oxygen's normal. The cables are functioning. We're just...
MACKIE: Cut off. On our own.
SINGH: Ah! What's happening?
(Clatter, jolt, rumble.)
MIN TSO: We've stopped. And the pressure on the hull is 1,200hPa.
BARCLAY: What, is that... is that good or bad?
MIN TSO: Well, that's like sea level. That's the pressure on land, except we're five miles down.
SINGH: Five miles.
BARCLAY: So, what, are we inside something?
(It goes dark.)
SINGH: Argh!
MIN TSO: The whole system's gone down!
CAMPBELL: Oh, my God...!
PIERCE: Helmets on, everyone.
MACKIE: Backup should kick in any second.
CAMPBELL: This is a trap! They're going to kill us!
PIERCE: For Christ's sake, Ted! Shut up!
CAMPBELL: Oh, that's it? That's backup?
MIN TSO: There's something at the hatch.
SINGH: It's them!
MIN TSO: They're breaking in!
PIERCE: Brace positions!
(The hatch seal is broken. No water, no compression.)
BARCLAY: Who's going first?

[Outside the submersible]

PIERCE: Yeah...
MIN TSO: Is it a cave?
PIERCE: I don't know. Wait there.
(The floor is covered in water. Barclay trips.)
BARCLAY: Oh! Ah, bloody hell. It's alive.
(The roof is moving in a current.)
PIERCE: Temperature's 21 degrees Celsius, which is... impossible. The atmosphere's breathable. Not just breathable, it's perfect.
BARCLAY: This place is incredible.
PIERCE: You can come out now. Be careful, there's a drop.
BARCLAY: It's some kind of membrane. There's got to be billions of tonnes of water behind this. One tear in that membrane...
PIERCE: Watch your step, the ground's uneven. If this is the ground.
(Brief purple light.)
SINGH: Ah...! What the hell was that?
MIN TSO: Decontamination?
PIERCE: Everyone okay? Okay?
CAMPBELL: What is this place?
BARCLAY: It's like... nothing in the world.
CAMPBELL: It's like hell.
SALT: Welcome.
BARCLAY: Where exactly are we?
SALT: Deeper than any human has ever been. You can remove your apparatus.
PIERCE: No, wait.
SALT: This environment has been prepared for you. Will you trust me, Barclay?
BARCLAY: Yeah.
(Salt removes his helmet as they gaze deep into each others eyes.)
BARCLAY: It's okay.
(The other remove their helmets, except Campbell.)
SINGH: The roof's leaking!
SALT: There is no roof.
CAMPBELL: What?
SALT: But you are safe.
CAMPBELL: Er... Yeah, I'd prefer to keep this on.
SALT: As you wish.

[Corridor]

(Kate is shaking.)
IBRAHIM: It's fatigue. You're running on empty. All this pressure, it's taking its toll. Pretty soon, you're going to be of no use to anyone.
KATE: I feel fine.
IBRAHIM: After 48 hours, the brain and the body start to shut down. I've seen it happen, and I'm watching it happen to you. If I reported you, you'd be escorted from the building.
KATE: Except you wouldn't do that.
IBRAHIM: The delegates are miles beneath the surface in radio silence for hours. There's nothing else you can do right now. But soon as they're back, we need you on form, rested and ready for whatever comes next. You're amazing. But you're not invincible. Either I take you home to rest or I report you.
KATE: My apartment is a fully-equipped comms hub. I'll work from there.

[Tunnel]

PIERCE: So, how is it light down here?
MIN TSO: Well, many deep-sea organisms are bioluminescent - bacteria, plankton, species of fish.
PIERCE: So, are we, er... inside an organism or...?
MIN TSO: I have no idea.
BARCLAY: This is impossible.
SALT: Your world of steel and glass and sunlight is equally impossible to us.
BARCLAY: And is this... is this is where you live?
SALT: No. We are nomads. All of the oceans and waterways are our home. They are curious, that is all.
(Other species are looking through transparent membrane.)
BARCLAY: So, do you all live here together? Like, all the species?
SALT: There are the fish, there are the titans, the dolphins... ..and us.
BARCLAY: Ah, so it's er... it's like a hierarchy, then? Like a class system?
SALT: There are degrees of intellect. Do not assume we think as one.
MIN TSO: Oh! Oh, so...
SINGH: Sorry, sorry. I... I just er... This is a lot, and...
MACKIE: Here, hold on to me.
PIERCE: Come on, come on. Keep moving, keep moving. Come on.
BARCLAY: Hang on, where are the others? Have the walls moved?
SALT: It's just you... and me.
BARCLAY: I feel like I know you... or I'm going to know you... or I've known you forever. Is that weird?
SALT: I understand. You're so warm. And rough.
BARCLAY: Can I er... Can I touch you?
SALT: What do you feel?
BARCLAY: Strength... and beauty. I don't know why you chose me for any of this.
SALT: The tides have drawn us together. The undercurrents pulling us closer. If you calm your mind. you'll feel their power. But your thoughts are noisy.
BARCLAY: Can you read them?
SALT: Human emotions are so loud, we cannot help but listen. Your heart is racing.
BARCLAY: Yeah, I don't want to mess this up. Billions of people are counting on us.
SALT: You have good intentions. We could make a difference, you and I. End the conflict between our species... before it's too late.
BARCLAY: Yeah.
PIERCE: Barclay! We thought we'd lost you. Are you all right?
BARCLAY: Yeah.
SALT: We are assembled.
SINGH: Oh, my God!
SALT: Do not be afraid.
BARCLAY: This is how it felt for you, meeting us.
(A huge chamber, with hundreds of aquatics on many platforms.)
SALT: Welcome to our domain.

[Kate and Ibrahim's apartment]

(Kate is sitting on the sofa, with her laptop.)
KATE: They're down there, on their own, with no support.
IBRAHIM: Do you think, one day, we won't need to keep us a secret any more?
KATE: I don't know.
IBRAHIM: I'm sick of hiding it, pretending, worrying about being transferred to God-knows-where.
KATE: Alaska?
IBRAHIM: Huh. You find it so easy.
KATE: The future of the human race pivots on what happens tonight. We don't matter. How can you be thinking about us?
IBRAHIM: I think about us all the time. Can't you not be commander-in-chief, just for a few hours?
KATE: I don't know how.
(Telephone.)
IBRAHIM: Leave it.
KATE: Shirley, hi. Any news from the delegates?
SHIRLEY [OC]: No, all quiet.

[Control room]

SHIRLEY: So, I ran some intel on the people in that COBRA meeting.
KATE [OC]: Thanks.
SHIRLEY: I think I found something. A repeated word in diplomatic communications. Does the word Severance...

[Kate and Ibrahim's apartment]

SHIRLEY [OC]: ..mean anything to you?
KATE: No.
SHIRLEY [OC]: It's never appeared before, now it's been used 14 times in the last two days.

[Control room]

SHIRLEY: Coded messages going back and forth. "Severance," "Severance," "Severance..."
(A red dot appears on Kate's forehead. Ibrahim pushes her out of the way as the balcony door class shatters.)
SHIRLEY: Kate?

[Kate and Ibrahim's apartment]

SHIRLEY [OC]: Kate, are you there? Kate? Kate? Kate? Kate, are you there?! Kate!

[Chamber]

CAMPBELL: This is for you.
(He holds out the globe. It starts to glow red.)

[Kate and Ibrahim's apartment]

(Ibrahim took the bullet. Kate tries to staunch the chest wound.)
KATE: All right, you breathe. You keep breathing. All right? All right. I'm going to get help. Darling, stay with me. Please, don't go! Please, don't leave me! Don't... leave! I love you!

[Chamber]