The Master (Sacha Dhawan) talks the Doctor (Jodi Whittaker) into joining him in the ruined Gallifrey, where he forces her to enter the Matrix. He reveals to her the secret history of Gallifrey and its native Shobogans. A space-explorer named Tecteun (Seylan Baxter) discovered a Timeless Child with the ability to regenerate. She adopted the child and reproduced her regenerative powers for the Shobogans, who became the Time Lords. The number of regenerations was limited to twelve, but this Doctor is the Timeless Child and is not limited to that. She and Tecteau were inducted into the secret “Division”. Knowledge about the Division was redacted from the Matrix and the Doctor’s memories were replaced.
With the Doctor trapped in the Matrix, the Master lures the Cyberleader Ashad (Patrick O’Kane) to Gallifrey and miniaturizes him, taking control of the Cyberium. He creates a race of regenerating Cybermen in order to take over the universe. In the Matrix, a vision of the fugitive Doctor (Jo Martin) restores the Doctor’s belief in herself and she escapes the Matrix by overloading it with memories of all her past incarnations.
On the Cyber-Carrier, Bescot (Rhiannon Clements) is killed, while Yaz (Mandip Gil) and Graham (Bradley Walsh) hide from the Cybermen in empty cyber-armour. They save the lives of Ryan (Tosin Cole), Ethan (Matt Carver), and Ko Shamus (Ian McElihinney). They gather to go through the portal to Gallifrey.
The Doctor joins her companions and discovers that Ashad’s miniaturized body contains a Death Particle capable of destroying all life on a planet. They blow up the cyber-carrier, destroying Ashad’s army and foiling his plans. She sends her allies home in an unused TARDIS and sets off Ko Sharmus’s particle. She escapes in another unused TARDIS as the explosion consumes Gallifrey. The companions land successfully on Earth, but the Doctor is arrested by the Judoon and imprisoned inside an asteroid.
The episode was written by Chris Chibnall and directed by Jamie Magnus Stone, as was the previous episode. It received mixed reviews and was controversial because it played somewhat fast and loose with Doctor Who continuity and canon, though Jodie Whittaker’s dynamic performance was praised. It was a powerful and epic season-ender. Nicholas Briggs, as usual, was the voice of the Cybermen. When the Doctor and the Master arrive in the ruined Gallifrey, the Master says, “Look upon my works, Doctor and despair,” paraphrasing an 1818 sonnet by Percy Bysshe Shelley called Ozymandius.
Many Doctors, companions, and villains appear out of the Doctor’s memories. Some had been hinted at in the Brain of Morbius episode from Tom Baker’s era. They were supposedly incarnations from before the First Doctor, which was inconsistent with the rule that Time Lords could only regenerate twelve times. This inconsistency was ignored for 44 years until this episode reconciled the two ideas, by suggesting that these early incarnations were that of the Timeless Child. This intrigued many fans and outraged others.