On Gallifrey, the Doctor (Peter Capaldi) has escaped from the castle in which he was imprisoned for more than four billion years. Aided by the military, who think of him as the warrior who saved Gallifrey, he exiles Lord President Rassilon (Donald Sumpter) and takes over. He learns that it was Rassilon who imprisoned him. The purpose was to make him confess his knowledge of the Hybrid, as it is prophesied to unravel the web of time. He makes the Time Lords snatch Clara out of time just before her death, then steals the TARDIS and takes her away. This may well damage Time itself. After travelling to the end of the universe, he finds the immortal Achildr (Maisie Williams) waiting in the ruins of Gallifrey. She thinks that the Hybrid is the Doctor and Clara together. He wants to erase Clara’s memories of him so the Time Lords can’t find her. Clara will accept her death, but not the loss of her memories of the Doctor. The Doctor admits that he became the Hybrid by trying to save Clara.

Clara reverses the procedure, and his memories of Clara are erased, because he is half-mad, and this may cure him. In a diner in the Nevada desert, he talks about Gallifrey to a waitress, who is Clara, but he doesn’t recognise her. The diner is the outside of a TARDIS that Clara and Asildr stole, and they leave in it. The Doctor leaves in his own TARDIS, with the brand-new sonic screwdriver it made for him.

The interior of Clara’s and Ishildr’s TARDIS is that of the original as it appeared in the first Doctor Who story. The Doctor visits the old barn on Gallifrey that was featured in other episodes. When Ashildr knocks on the TARDIS doors, she knocks four times. The Doctor erased the memory of Donna Noble. He recognises the diner as the one he visited with Amy Pond and Rory Williams. A bit of the music from the Good, the Bad, and the Ugly is heard, and a bit of the Ninth Doctor’s theme. The story received positive views in general, though some wondered why Clara should come back after her dramatic death. The Doctor is quite mad after losing Clara and being tortured for millions of years. He gets his revenge on Gallifrey, overthrows the President, threatens time itself, and saves Clara, but is forced to forget her. The ending is quite touching.