The Doctor (Jodie Whittaker) and Yaz (Mandip Gill) are after Karvanista (Craig Els) who is a dog-like Lupari alien, though Yaz is not quite clear why they are chasing him. He captures them and hangs them over a sea of acid, but they escape and follow him to Earth in the TARDIS. The Doctor has a psychic vision of Swarm, a mysterious evil being escaping from its 1000-year imprisonment by the Time Lords’ secret Division.
In Liverpool, Dan Lewis (John Bishop) arranges a date with a museum worker named Diane before working a shift at a soup kitchen and heading home. Karvanista breaks into his house and transports him onto his Lupari ship. The Doctor and Yaz arrive after his disappearance and discover what appears to be a Lupari invasion fleet nearing Earth. They escape just before the house implodes. Then they meet Claire (Annabel Scholey), who claims she met the Doctor in the future. As the Doctor and Yaz leave, they find an extra door in the TARDIS control room. Claire is captured by a Weeping Angel. Confused yet?
On Karvanista’s ship, Yaz rescues Dan as the Doctor confronts Karvanista over his connection to the Division. Karvanista reveals that the Lupari are actually saving Earth from destruction by the Flux, an unknown entity that defies all the laws of Space and Time and consumes everything in its path. The Doctor, Yaz, and Dan escape the ship and return to the TARDIS to investigate the Flux. And there is now a third door in the TARDIS control room.
The flux causes Vinder (Jacob Anderson), the only crew aboard a remote outpost in Deep Space, to evacuate his position, and catches the attention of the Sontarans, always anxious to cause destruction. Swarm (Sam Spruell) attacks a base in the Arctic Circle, killing one crewmember and reviving Azure (Rochenda Sandall), who lures Diane into a derelict house. Karvanista is last of the Division, who erased the Doctor’s memory of being the Timeless Child. Now, you’re confused.
The TARDIS takes them all to an area of space where they can observe the Flux from a distance. The Doctor has another vision of Swarm, who claims to know her well. The Flux accelerates its attack on Earth before the Lupari fleet can rescue the population. The Doctor has Karvanista form a defensive shield with the Lupari ships, protecting Earth from the Flux. But the TARDIS is unable to pass through the shield. The three doors of the TARDIS fly open as the Flux approaches. The Cloister bell, warning of destruction, is heard.
The episode was written by showrunner Chris Chibnall. You found it confusing because it was the first part of a six-part story entitled Flux and they introduced all the characters and sub-plots in this one episode. But it was quite popular and moved at a breakneck speed.. Jodie Whittaker and Jacob Anderson (Vinder) worked together on six episodes of Broadchurch. The Doctor, trying to escape from handcuffs she set up when she had a Scottish accent, uses the voices of Peter Capaldi and Sylvester McCoy. This is the first time the Doctor Who show ever tried a six-part continuous story. It might make more sense if it could be seen streaming for six episodes at once, but to wait an entire week before each new development was a bit of a stretch.