Former TARDIS companion Mel Bush (Bonnie Langford) helps the Doctor (Ncuti Gatwa) escape from Susan Triad (Susan Twist), a minion of the evil God of Death, Sutekh (Gabriel Woolf). Susan and Harriet Arbinger (Genesis Lynea) kill everyone by releasing Sutekh’s poisonous dust. The Doctor and Mel meet up with companion Ruby Sunday (Millie Gibson) in the Time Window as Sutekh arrives on top of the TARDIS in the form of a huge dragon. He reveals that when the Doctor defeated him previously, he latched onto the TARDIS and grew even more powerful. His dust is spreading through every place the TARDIS has ever landed through copies of Susan. The Doctor realizes that he and Ruby can use memories to create a remembered TARDIS which they and Mel use to escape, but death spreads throughout the galaxies.
The Doctor uses intelligent rope to stabilize the remembered TARDIS. He visits a woman who gives him a spoon with which to repair a monitor from the Time Window. It responds to Ruby’s memories and shows her a 2046 interview with Roger ap Gwilliam (Aneurin Barnard), the most dangerous Prime Minister in History. Because Gwilliam made DNA tests compulsory, they can find Ruby’s birth mother. Sutekh is only keeping them alive because he wants to find Ruby’s mother too.
The Doctor, Ruby, and Mel visit the year 2046 and search the DNA records for Ruby’s mother. Mel, unfortunately, is turned into a minion of Sutekh and everyone is transported back to UNIT HQ. Sutekh attacks the Doctor and, to save him, Ruby says she will show Sutekh the name of her mother. Instead, she destroys the monitor that contains the information and attaches the intelligent rope to Sutekh’s collar The Doctor uses a whistle to draw the TARDIS toward him, killing Harriet, and attaches the other end of the rope to its console, which drags Sutekh through the Time Vortex in a spectacular scene, undoing his evil as it goes. Then, he releases him into the Time Vortex, where he is lost forever.
Susan joins UNIT, who identify Ruby’s birth mother, Louise Miller (Fye McKeever), who was just a 15-year-old girl at the time. The Doctor reunites Ruby with her mother. Ruby decides to visit her father as well, and the Doctor departs after saying good-bye. Mrs. Flood (Anita Dobson) explains to the audience that Ruby has a happy ending, but the Doctor is headed for misfortune.
The episode was directed by Jamie Donoughue and written by Russell T. Davies. It is a sequel to The Legend of Ruby Sunday and the final episode of the Fourteenth Series. Sutekh was an amalgam of various evil forces from various cultures, using things like a virtual reality headset. Much of the episode was filmed in Cardiff, Wales, using a red double-decker bus, a telephone box, and a London Cab to make it look like London. Replicas of the TARDIS from the Tom Baker years and clothing from the sixth and seventh Doctors were used. Bonnie Langford was transformed into a minion of Sutekh with prosthetics. The episode garnered 80% on Rotten Tomatoes, though there was criticism of some of the plotting and it was thought not quite amazing enough for a season-ender. I thought it was creepy and spectacular, particularly the dragon-like giant Sutekh and the scenes in the Time Vortex, which we usually only see in the opening montage.