Doctor: Jodie Whittaker
Bradley Walsh (Graham O'Brien)
Mandip Gill (Yasmin Khan)
Tosin Cole (Ryan Sinclair)
Ian Gelder – Zellin
Buom Tihngang – Tibo
Clare-Hope Ashitey – Rakaya
Sharon D. Clarke – Grace O'Brien
Bhavnisha Parmar – Sonya Khan
Aruhan Galieva – Tahira
Sirine Saba – Maryam
Nasreen Hussain – Anita Patel
Everal A Walsh – Gabriel
Michael Keane – Fred
Amanda Liberman – Mum
Willie Jonah – Old Tibo
Anthony Taylor – Andrew
Directed by Emma Sullivan
Written by Charlene James, Chris Chibnall
Script editor: Fiona McAllister
Produced by Alex Mercer
Executive producer(s) Chris Chibnall, Matt Strevens
Incidental music composer: Segun Akinola
Length: 49 minutes
First broadcast 9 February 2020
The Doctor drops her companions off in Sheffield to spend time with friends and family, while she responds to an alert from Aleppo, Syria in 1380. There, she saves Tahira, the last patient alive in a mental hospital, from a threatening creature.
Meanwhile, the Doctor's companions have dark visions: Graham sees a trapped woman pleading for help; Yaz has nightmares about a man in dark clothes, and Ryan sees the same man detaching his fingers and placing them in his friend Tibo's ears after which they both vanish. The three contact the Doctor simultaneously.
The Doctor uses the TARDIS' telepathic controls to track down Graham's vision, locating it as a spacecraft lodged between two planets, preventing the planets from colliding. Inside the craft is a small prison structure with a power source protected by a quantum fluctuation lock. They also find signals being sent from Earth to the prison via the detacted fingers. The Doctor manipulates the lock while the others explore the craft, but are captured by the dark-clothed man. Just as the Doctor opens the lock, the man reveals himself to the Doctor as the immortal god Zellin, and thanks her for rescuing his ally, Rakaya, another immortal god that had been trapped in the prison. The two thrive in causing chaos, and had turned the civilizations on the two planets against each other before its inhabitants learned how to trap Rakaya. To keep her sane, Zellin sent her nightmares from humans on Earth.
Zellin and Rakaya trap the Doctor and travel to Earth to feed off nightmares. The Doctor frees herself and her allies, and discovers how to manipulate Zellin's fingers to engage the prison. Knowing that the creature in Aleppo is a nightmare from Tahira's own mind and cannot harm her, the Doctor lures the gods to Aleppo, and then traps the gods and the creature in the prison.
After returning Tahira to her time, the others return to contemporary Sheffield to recover. Yaz goes to thank a police officer who had talked her down from suicidal thoughts years prior. Graham opens up to the Doctor about his past cancer scares. Ryan talks to Yaz about the impact of their travels with the Doctor on their personal lives. As her companions discuss their future with the Doctor, she suddenly announces they are going to visit Mary Shelley.