S03E13: 'The Last of the Time Lords'

A year has passed since the previous episode, with Martha roaming the world, Captain Jack locked up and the elderly Doctor kept in a cage by The Master to observe the human race heading towards extinction. The Master is building warships to conquer the rest of the universe, claiming that he has created a new Time Lord Empire. Meanwhile, Martha - using the Tardis key perception filter to be unseen - is trying to find a way to beat the evil adversary and hooks up with rebel Thomas Milligan and Professor Doherty.

The Master is aware of Martha's survival and sends out a video message in which he ages The Doctor by 900 years into a tiny, pathetic creature. Martha at least knows her friend is still alive. Martha tells her new associates that the Toclafane can be conquered by lightning and they capture one by using a lightning strike after leading it into a trap. They open it up and discover a shrunken human from the end of time and the Utopia project. The Master brought them back in time to kill off their own ancestors, making it possible by cannibalising the Tardis and setting up a paradox machine.

Martha tells Doherty that she can kill The Master using a gun - needing four separately located chemicals - developed by UNIT and Torchwood. She needs one more chemical, to be found in London, and sets off with Milligan. Doherty then reveals herself as a traitor by informing The Master of Martha's plans, in return for information on her family.

Martha is captured and taken to The Master's airborne ship The Valiant and Milligan is killed. As the clock counts down before the launch of the fleet, Martha reveals that her real mission - whispered in her ear a year ago by The Doctor - was to spread the word around the globe about her Time Lord friend and gather the entire globe's psychic energy and think of him at a certain time. The Doctor is able to harness this energy by mentally tuning into his ultimate foe's Archangel network and he is returned to his former, healthy state.

The Master, thwarted, threatens to blow up his warships and thus the planet. But Jack has managed to destroy the paradox machine on board the Tardis and thus time is reversed to before the arrival of the Toclafane. The Doctor forgives his foe and says he will keep him in the Tardis and monitor him, but Lucy Saxon takes matters into her own hands and shoots him. The Master, despite The Doctor's pleas, refuses to regenerate and dies, claiming victory in the process. He is later cremated, but a female hand picks up his ring from the ashes.

Captain Jack opts to return to Torchwood, randomly mentioning that he once picked up the nickname The Face of Boe, which fits in with the fact he is immortal. Martha, not happy that her love is not returned, opts to stay on Earth with her family and gives Milligan a call. The Doctor sets off on his own, but suddenly the bow of the Titanic crashes through the wall of the Tardis...