Trama

Having decided that everyone could do with a holiday, Graham accidentally teleports himself, Doctor, Yasmin, and Ryan to a luxury resort for a spot of relaxation. However, they discover the place where they are having a break is hiding several deadly secrets. What are the ferocious monsters that are attacking Tranquility Spa?

The Doctor and her companions are cleaning up in the TARDIS after a deep space squid's mating season, and Graham says he got his sixth coupon to collect a free holiday at Tranqulity. Yasmin says that a holiday might get the Doctor out of her mood, and the Doctor insists that her mood is fine. Graham puts the six coupons together and the Doctor is too late to warn him to stop. She says that it's a teleport cube, and four seconds later they're all teleported to Tranquility.

The group materialize on Tranquility Spa and a woman, Hyph3n, welcomes them. She says that they can return to the TARDIS at any time and their room are being prepared, and invites them to take a moment to explore. Yasmin goes to the pool and Ryan explores inside, and Graham prepares to sit. A lot. The Doctor goes off to have a look around by herself.

A system virus infiltrates the spa computer system, and Vorm and Kane tend to it. Kane tosses Vorm a gun and tell him not to engage without her.

Two guests, Benni and Vilma, sit by the pool and Yasmin joins them. Bennis is preparing to give his companion Vilma an engagement ring but puts it away when Yasmin interrupts.

Ryan goes to the bar and checks a vending machine. It shocks him and when the Doctor comes in, says that the machine has a hopper virus and passed it on to him. Ryan's legs go out and the Doctor catches him as he collapses, and Ryan then coughs up a virus which the Doctor catches in a crisps bag, then tells Ryan to suck on his thumb until the hallucinations stop. As Ryan swings at bat hallucinations, the Doctor assures everyone that he's fine.

Kane gets another warning from the computer and warns Vorm over the radio that it's on the move

Benni and Vilma introduce themselves as the computer voice tells everyone to gather at their nearest muster station for a routine Tranquility drill. The Doctor is carrying Ryan and drops him, deciding to investigate. Ryan sees another woman sucking her thumb like he is. He chats with the woman, Bella, who says that she's a hotel critic. Ryan claims that he's a surgeon for pilots, and Bella figures that he's pretending to be stupid. He insists that he's not trying to chat her up, and Bella says that it's a shame and introduces herself. Vorm goes through saying that he'll isolate it in the east zone, and Ryan and Bella follow him to see why he has a gun.

The Doctor finds Hyph3n and asks her about the hopper virus. She figures that it's a weapon and someone is targeting Tranquility, and notes that an alarm is going off. Hyph3n is going through a door and the Doctor asks what's on the other side and wants to take a look. She flashes her psychic paper, claiming that she's an inspect6ion officer, and Hyph3n finally takes her in. Kane asks why Hyph3n brought the Doctor in, and the Doctor notes that the hopper virus mutates system and the spa's ionic membrane has failed. She then wonders why they're defending a spa with an ionic membrane.

Vorm opens fire at something, and a guest crawls toward him and is then pulled around the corner. Vorm tells Kane that it's attacking the guests, and Kane tells him that she's en route and he shouldn't engage. Hyph3n wants to engage teleport evacuation but the Doctor warns that the hopper virus has disabled the systems and demands an explanation so she can help.

The lights go out in the hallway Vorm is occupying, and alien creatures advance on him. Ryan and Bella hear the creatures and hide.

Graham enters the bar and tells the repairman, Nevi, who is with his son Sylas. Nevi tells Graham that nothing is working and argues with Sylas over which tool to use.

Kane shows the Doctor a schematic of Tranquiltiy and the 23 guests. Two of them go off-line, and the Doctor tells the guests over the tannoy to gather at the control room in the north corridor immediately. She insists that it's not a grill, and Graham, Nevi, and Sylas hear the guests screaming.

Ryan and Bella go to the Tranquility steam room and a guest runs in, saying that they're coming. They all hide, and Ryan and Bella admit to each other that they're not who they claimed earlier. One of the creatures enters the steam room.

The Doctor feeds in a debug script to stop the hopper viruses and tells Kane that she needs more time to rebuild the ionic membrane.

Yasmin, Benni, and Vilma go to the bar and Yasmin compares notes with Graham. Hyph3n takes them into the control room. Benni goes back to get Vilma's hat and a creature growls at him.

The visuals go out across the compound and Vorm returns and tells Kane he couldn't stop it. He warns that the creatures are heading for the guest teleport, and Vilma notices that Benni is gone. Yasmin wonders where Ryan is.

The guest in the steam room panics and runs, and the creature kills him.

The Doctor activates the ionic membrane, exiling anything with alien DNA. Meanwhile, the creature advances on Ryan and Bella... and the membrane exiles it. Red dots come up the schematic, and Vorm says that they're casualties of the Dregs.

Bella wonders what happened, and Ryan figures the Doctor did something.

Graham goes out to find Ryan, and Nevi and Sylas follow him. Vilma notices that Benni isn't on the schematics,

Ryan and Bella come out of the steam room and Graham finds them. He hugs Ryan in relief. They go outside with the Doctor and Kane, and Kane explains that the local Dregs got in. She figures that someone hacked the systems since the Dregs couldn't have. Kane has Vorm activates a void panel, revealing that the spa is surrounded by a fake-cation. The Doctor realizes there's a completely different environment outside and the native species wants the spa occupants dead. Yasmin and Vilma arrive and Yasmin has used a scanned to confirm Benni is outside the shields. Vilma notes that Benni has an oxygen tank and could still be alive, and insists on finding him. The Doctor says that Benni came there because of Kane and they'll help, and goes to get the surviving guests.

In the bar, Kane hands out O2 canisters and tells everyone to watch the readings and stay in the truck until she says otherwise. Sylas helps Graham adjust his breather, and Nevi goes to start up the truck. The Doctor demands answers and Kane says that they're on the planet Orphan 55. Kane insists that the radiation dropped and the orphan planet is safe for short spells, and goes to the truck.

The truck takes off across the barren planet, and the Doctor tells her companions that the planet is graded "orphan" because the environment is too toxic for life. The ruling society gets to evacuate and write off anyone left behind. Kane explains that they can eventually terraform Orphan 55 with the proceeds from the visitors. Graham discovers that Benni has changed location and Kane tells Vorm to abort the mission. She figures the Dregs have Benni, and Vilma insists on getting him back. She gives Kane a necklace worth a fortune and the Doctor says that a man's life is at stake. Kane takes the necklace and tells Vorm to follow the tracker.

As they continue, Kane refuses to tell the Doctor about the Dregs. The Doctor deduces that the Dregs somehow lived through the fallout, and Kane is equipping her laser with a modulator against something that can adapt to the beam. The Time Lord realizes that the Dregs are highly-adaptable apex predators and they're driving into the creatures' territory.

As the truck continues following Benni, Ryan asks Bella how long she's been unemployed. Bella finally says that she was her father's carer but he died. Ryan mentions that his mum died eight years ago, and Bella says that her mother was worse than Nevi. The Doctor sits between them and asks what's going on, and Ryan tells her that they were just talking. Yasmin is down the truck and asks Ryan what he was talking about.

The truck shakes and grinds to a halt, and the Doctor and Kane go outside. The Dregs set a trap to stop the truck, and Kane warns that when the sun comes out in ten minutes, they'll suffer solar blistering and then death. Kane finds a service tunnel on the map and says that if they can reach there, they might live. Vilma insists that they have to continue, but Kane ignores her and tells everyone to follow her.

The group heads for the tunnel, and Yasmin silence Vilma when she calls to Benni. The Dregs mass around them and move in, and the Doctor orders everyone back to the truck. Once inside, Ryan and Bella bump fists. The Dregs move in on the truck and scrape at the walls, and Kane tells the Doctor to get everyone to the tunnel while she and Vorm keep the Dregs busy.

Benni calls to Vilma from outside, and warns that he doesn't have long. He asks Vilma if she'll marry him, and Vilma yells that she will. Benni then asks for anyone to shoot him if they can. The Dregs pry open the roof panel, and Kane and Vorm run out to fire on the creatures. The Doctor and the others exit through the bottom hatch and head for the service tunnel. Hyph3n is last and a Dreg grabs her before she can get out. The group finds a wounded Kane, who wants to stay and help Vorm. The Doctor tells her that they need her knowledge of the tunnels, and they get into the service tunnel.

Kane checks the tunnel and says that there's a short-range maintenance teleporter that should get them back to the spa. Vilma asks Kane if she saw Benni, and Kane says that she killed him because he asked her to. Vilma is shocked and Graham leads her gently away, and Kane tells the Doctor that the Dred was having fun torturing Benni. Bella grabs Kane's gun and demands to know where the maintenance teleporter is. When Ryan wonders why Bella is threatening Kane, Bella explains that she's going to burn the place down and Kane is her mother that abandoned her. Kane tells her where the teleporter is, then draws her gun.

The Doctor steps between them and suggests they discuss thing. A Dreg enters the service tunnel, and Ryan shoves himself and Bella into the teleporter. They arrive at the spa, and Bella refuses to help the others, saying that if Ryan isn't with her then he'll die when she destroys the spa.

The Doctor locks everyone inside of a storage cage. Kane says that there are stairs nearby but they'll have to go through a Dreg nest to get to them. The group get out as the Dregs start to break through the metal. Kane tells the Doctor that she didn't know Bella was there, and Yasmin points out that Kane left Bella and her father. The woman says that she was only working on Tranquility to give it to Bella, and the Doctor suggests she should have mentioned that to Bella before drawing a gun on her.

At Tranquility, Bella reveals that she smuggled a bomb in and it's not her first.

As the group's air runs out, Vilma worries that she's slowing them down. The Dregs move in on them, and the Doctor finds a sign in Russian. They realize that they're on Earth and they're in a Russian underground station. They take cover with the others, and Vilma tells them to run and stay alive. She then steps out, yelling and waving her arms, and the Dregs tear her apart as the others run.

Bella plants another hopper virus and aims a gun at Ryan when he tries to stop her. She says that she will shoot Ryan if he gives her no choice. As Ryan tells her to shoot him, a small bomb that Bella planted in the bar goes off, and she realizes that she blew up the mainframe.

The survivors enter the Dreg nest and Kane warns that they have to go through silently to avoid waking up the sleeping Dregs. Graham assures Yasmin that Vilma died so they could escape. The group get to the stairs up to Tranquility, but Graham realizes the Doctor is gone. The Doctor has hung back as her oxygen supply runs out, and refills her oxygen supply from the breath of a sleeping Dreg. She mentally scans the Dreg and sees memories of nuclear devastation.

The Dreg wakes up and grab the Doctor by the throat. Kane comes back and shoots it, and the Doctor runs to her and says that the Dregs breath in CO2 and breath out oxygen. As the Dregs move in, Kane throws a flare to draw their attention and says that she owes all of them for starting it. She asks the Doctor to tell Bella that she's sorry, charges the Dregs, and goes down fighting.

The others break into what's left of the bar. The Doctor joins them and they close up the grille to the stairs, as the Dregs come up. Ryan and Bella run in, and the Doctor tells everyone to get to the command station while the Doctor, Ryan, Graham, and Yasmin hold the grille shut. Ryan sees a "Made in China" sign on it, and the Doctor explains that they're in Earth's future. The Dregs are the few mutated humans that didn't die, and the Earth was destroyed by global warming and the collapse of the food chain.

The Doctor tells everyone to run, and when they do the Dregs break through. They join the others in the control room, and the Doctor tells Bella that Kane didn't make it. Sylas tries to help Nevi and complains when his father doesn't listen to him because he's too busy. Yasmin spots the Dregs outside the dome on the surveillance system, and the Doctor realize that they're massing for an attack on the membrane. The Doctor tells Nevi to fix the teleporter, and he says that they need Syrillium 4 to power up the teleporters and get off the planet. The Doctor remembers that Syrillium 3 mutates into Syrillium 4 when attacked by the hopper virus.

Angry, Sylas goes out in the corridor, sealing the command center door behind him. He runs, and inside the control center, Bella figures they're all going to die there. The Doctor figures that the Dregs hate oxygen, and the dome is air-conditioned so if she ups the oxygen levels, it will weaken the Dregs. She tells Yasmin and Ryan to keep the Dregs at bay at the steam room where Tranquility meets the dome wall. The Doctor tells Graham to stay with Nevi, and she goes with Bella to find Sylas. When Bella wonders why she should follow the Doctor's orders, the Doctor tells her that she caused the mess and now she's going to help fix it.

Graham and Nevi go outside to get the Syrillium 3 from the drive core.

Ryan and Yasmin go to the steam room and barricade the wall to keep the Dregs out.

The Doctor and Bella search for Sylas and find him... and a Dreg nearby.

The Dregs break in through the steam room wall, and Yasmin grabs an air hose to drive them back. The oxygen in the steam drives them back.

The Dreg moves toward Sylas from a nearby cage, and the Doctor tells Bella to grab Sylas and take him to the teleport pad while she distracts the Dreg. As she taunts it, it steps into a CO2 outlet and hesitates. The Doctor realizes how to isolate it and tells Bella to go with her.

Nevi wishes Sylas was there because he would know what to do. Sylas comes out, and father and son hug. The boy then goes to work making Syrillium 4.

The Dregs move in despite the oxygen, and Ryan leads Yasmin off.

The Doctor gets Bella into the cage with her, figuring that "Wheezy" is the Dreg leader. She sonics the room door closed and tells Bella they'll deny it the CO2 that it needs. The Doctor talks to Wheezy, saying that it can hear her because she was in its head. She tells it that they currently have a perfect ecosystem and if the Dregs kill them, they'll die as well. The Doctor says that Wheezy has to let them go if it wants to live, and tells it to be smarter than the people who made it. After a moment Wheezy steps back, and the Doctor leads Bella out of the cage and says she's not going to open the outside door until Wheezy enters the cage. Once it does, the Doctor closes the cage and opens the outside door, and she and Bella leave. Behind them Wheezy goes berserk.

Ryan and Yasmin grab one of Bella's bombs and cart it down the corridor. They leave the bomb near the intruding Dregs and run off, and the Dregs approach the bomb as it counts down the last few seconds to 0.

Sylas puts the hopper virus into the Syrillium 3 as the others run out. The bomb explodes, destroying Tranquility, and Nevi warns it will take sixty seconds for the Syrillium to convert. As the Doctor speeds up the conversion with her sonic, Nevi warns that there are too many people to teleport. The Dregs come out, and Bella kisses Ryan then grabs a gun and prepares to shoot the Dregs. Graham holds Ryan, stopping him from going after Bella, and the Doctor teleports Nevi and Sylas away.

The gun fails and the energy backlash knocks Bella down. Kane runs up, grabs the gun, and yells at the Dregs to get away from her daughter. She helps Bella up and then tells Ryan that she's got it, and fires on the Dregs. Bella sucks her thumb, like she was when Ryan first met her, and he sucks his thumb back. The teleport finishes charging up and the Doctor sends herself and her companions to the TARDIS. Graham assures Ryan that Bella will be okay, but Ryan doesn't believe it.

Yasmin asks the Doctor when she knew that Orphan 55 was Earth, and the Doctor tells her that she knew just before Yasmin did. She tells them that it's one possible future, and admits that she can't tell them it will be okay. The Doctor insists that people have to face facts and deal with the coming catastrophe, but it's not decided. She tells them that people have to step up, and lives change worlds. The Doctor tells her companions to be the best of humanity.

On Orphan 55, a Dreg roars.