Doctor: Peter Capaldi (Twelfth Doctor)
Pearl Mackie (Bill Potts)
Matt Lucas (Nardole)
Kieran Bew – Ivan
Justin Salinger – Tasker
Peter Caulfield – Dahh-Ren
Mimi Ndiweni – Abby
Katie Brayben – Ellie
Directed by Charles Palmer
Written by Jamie Mathieson
Produced by Nikki Wilson
Executive producer(s) Steven Moffat
Incidental music composer Murray Gold
Series Series 10
Length 45 minutes
Originally broadcast 13 May 2017
The Doctor, Bill and an angry Nardole travel in the TARDIS to follow a distress call to a deep-space mining station. When the TARDIS is jettisoned by the station's computers, the trio are forced to wear "smartsuits", robotic spacesuits capable of independent operation tied to the station. The suits are also the only source of oxygen, as the mining company does not provide an oxygen atmosphere inside the station, and every activity is measured in breaths. The surviving crew warn them that some suits have received instructions to "deactivate" their "organic components", killing the wearer via an electrical discharge but remaining autonomous. This signal can be carried by touch, which has caused most of the crew to be turned into zombies, enslaved to the suits' programming. The Doctor and the others plan to walk outside the station to an uncompleted portion not updated in the computer systems to hide. Bill's suit malfunctions during depressurisation and forces her to remove her helmet. To save her, the Doctor gives her his helmet as they spacewalk. He survives the vacuum of space, but has gone blind from the ordeal.
The computer discovers their location, but as they flee, Bill's suit again malfunctions and will not move. The Doctor leaves her behind, assuring her she will not die. She is, however, electrocuted when the zombies touch her. The Doctor reveals the limit of breaths is an algorithm to stop people "wasting" oxygen, part of the company's automated profit-making system; killing the wearers was just the logical endpoint of corporate profit over human life. He hacks the station's systems to cause the station to self-destruct if they are killed, and convinces the others this is a "good death" and revenge against the corporation. The computers recognise this threat to corporate profits and recalculate the suits' programming, and the zombies turn over their oxygen supplies to the survivors. The Doctor then revives Bill, knowing that her malfunctioning suit did not have enough power to lethally shock her.
The TARDIS is recovered, and they drop the survivors off at their head office to confront the company; the Doctor notes there was a successful rebellion six months later. Nardole restores the Doctor's eyes, but when they return to the university and Bill departs, the Doctor reveals that he "can't look at anything ever again. I'm still blind".