Written by Jamie Mathieson, directed by Charles Palmer
“You only see the true face of the universe when it’s asking you for help.”
The Doctor, Bill and Nardole answer a distress call in deep space, and find themselves trapped on board space station Chasm Forge. All but four of the crew have been murdered – and the dead are still walking! In a future where oxygen is sold by the breath, and space suits are valued more highly than their occupants, the Tardis crew battle for survival against the darkest evil of all.
The Doctor is giving a lecture about how space wants to kill us. He explains the science and physics behind why you die quickly in space. At the end of the lecture, a student asks what it has to do with crop rotations. He responds that he doesn’t know, but space is cool. After the lecture, Nardole confronts him about missing space and thinks he is planning another adventure. They continue the discussion in the cellar, arguing about the fact that he is still there, guarding the vault, and that should be good enough.
Later, The Doctor and Bill are discussing where they will go on their next trip when he receives a distress signal, saying they will be going there to help. Nardole enters into the TARDIS. The Doctor tells him that he had sent him out on errands and he says that he saw through his “clever little ruse” and knew he was planning on leaving the vault again. He tells The Doctor that he removed the fluid link from the TARDIS and mentions that The Doctor told him that the TARDIS couldn’t work without it. The Doctor admits to lying about this and pulls the lever to take off, Bill laughing as they dematerialize.
They arrive on a space station. Discovering that there is no oxygen on the station, The Doctor increases the TARDIS bubble to cover the rest of the station. As they explore, they find a space suit containing a man who has been dead for some time. After a discussion about whether they should allow the suit to hold him up, they continue toward a noise they hear down the hall. They enter a room to find an empty suit performing menial tasks. The AI within the suit informs them that oxygen must be purchased by the breath and that any unauthorized oxygen will be purged. At this point, the doors open and the air in the room begins to be sucked out of the room. The Doctor uses his Sonic Screwdriver to close the door, blocking them off from the rest of the station. At this point, the suit holding the dead man begins to come toward them. The Doctor throws his Sonic at the suit, which short-circuits it and also breaks the Sonic. The AI informs them that they must put suits on in order to survive.
They put the suits on and receive contact from the remaining living passengers. Upon finding the passengers, they are informed that most of the crew has been killed, and The Doctor tells them that they have come in response to the distress signal. There is a “Bluish” named Dahh-Ren who is concerned about Bill being a racist. They have a discussion about prejudice and that she’s normally on the receiving end, which he doesn’t seem to understand.
An alarm sounds and they head down a corridor away from the oncoming crew-members. As the door opens, Ivan is hit by a suit, causing him to be killed by his own suit. The remaining team makes the decision to go outside to get into a new part of the ship, the location of which hasn’t been updated on the suits’ maps. As they are getting ready to leave the airlock, Bill’s suit malfunctions. The Doctor attempts to fix it and get her helmet back on but is unable to do it in time. The airlock opens and she passes out. When she wakes up, Nardole informs her that The Doctor was able to give her his own helmet, but was exposed to the vacuum of space for too long. He takes her to him and it is revealed that The Doctor is blind. As they discuss what to do next, the suits are able to update their maps and attack their current location, killing Dahh-Ren.
They run from the suits toward the communications center. Along the way, Bill’s suit malfunctions again and she is unable to move. The Doctor tells her that they have to leave her behind and she isn’t going to die. They leave her, causing her to get touched and electrocuted, and seemingly killed by the other suits. In the control room, The Doctor discovers that the rescue ship was sent out before the distress signal and that the suits were programmed to eliminate the crew when they became less profitable. The ship was their replacement, rather than rescue. He tells them that the best option at this point is to die well. When the suits enter the control center, he tells them that he has rigged the system so that, when they are all dead, the entire station will explode and the company will lose their entire investment, making it more expensive to kill them. The suits stop and give the crew their remaining oxygen tanks. At this point, The Doctor hits a button in Bill’s suit, reviving her. He explains that he had a chance to tamper with the suit, making the shock that was given a non-lethal one.
Back at the TARDIS, Nardole is busy fixing The Doctor’s eyes. He comments that he didn’t realize they had gotten back to the TARDIS. They go back to the university and Bill is sent on her way. Nardole scolds The Doctor about leaving the planet and tells him that things would be very bad if the occupant escaped. He asks what if he had come back injured, or had been killed, then yells at The Doctor to look at him when he’s speaking to him. He says that he can’t because he is still blind.