Survivors of the Flux
"Survivors of the Flux", prefixed frequently with either "Chapter Five" or "Flux", is the fifth and penultimate episode of the thirteenth series of the British science fiction television programme Doctor Who, and of the six-episode serial known collectively as Doctor Who: Flux. It was first broadcast on BBC One on 28 November 2021. It was written by showrunner and executive producer Chris Chibnall, and directed by Azhur Saleem.
The episode stars Jodie Whittaker as the Thirteenth Doctor, alongside Mandip Gill and John Bishop as her companions, Yasmin Khan and Dan Lewis, respectively.
Plot
The Weeping Angels transport the Doctor to a spacecraft carrying Division's head, Awsok from "Once, Upon Time", who is ordering an Ood to create a final Flux event. Awsok explains Division's involvement in the development of this current, and upcoming, universes. Division's spacecraft is travelling to another universe, as a "seed vault" containing genetic remnants of this universe. Awsok blames the Doctor for destroying this universe because the Doctor defected and interfered with Division's work. Thus, Division engineered the Flux to destroy this universe, with the Doctor still in it. Awsok reveals herself to be Tecteun, the Gallifreyan who found the young Doctor by a wormhole and raised her, while creating Time Lords. The Doctor blames Tecteun for robbing her of a life that could have been, but Tecteun counters that the Doctor does the same when she takes companions. Tecteun reveals the possession of a fob watch with the Doctor's lost memories.Dan, Yaz, and Jericho travel around the world in 1904 to try to discover the date for world's end, evading countless assassins. A Nepalese hermit suggests they should reunite with Karvanista; although they leave a message for him at the Great Wall of China, he cannot use time travel so cannot respond. The trio search out Joseph Williamson and the mysterious tunnels he dug under Liverpool, realizing he had discovered doorways leading to various time periods and locations.
In 1958, a general asks the Grand Serpent, going by "Prentis", to help form UNIT. Prentis embeds himself into UNIT leadership over the decades, eliminating potential threats to him. In 2017, when he closes UNIT down, Kate Stewart realises his deception and threatens to expose him. After a failed assassination attempt, she goes into hiding. With UNIT eliminated, in 2021 Prentis orders Earth's defences be lowered, inviting a second Sontaran invasion.
When a Lupari ship falls from Earth's shield, Karvanista recalls the missing Lupari ship stolen by Bel, just as she was arriving at the source of the Passenger signal. With Karvanista on board, Sontaran forces attack Bel's ship. Vinder also pursues the Passenger signal, arriving moments after Bel's ship is recalled, but finding kidnapped survivors being disintegrated by Swarm and Azure for use as a power source. As he intended, Vinder is captured by Swarm in a Passenger, where he meets Diane.
Swarm and Azure arrive on the Division spacecraft and plan on exacting revenge upon Division for imprisoning them. Swarm disintegrates Tecteun and approaches the Doctor to do the same.