Part two begins with a flashback to the last day of the Time War. The Time Lord Council has foreseen that the Doctor will have the opportunity to end the war by destroying both Daleks and Gallifrey, and will use that moment to do so. The President is adamant he will not allow himself or his race to die. An opportunity exists to prevent this, which involves placing Gallifrey and many other terrors in a Time Lock, and retrospectively implanting a link to the Master during his early childhood – the four-beat drum rhythm that has tormented the Master all his life. The connection can then be used to call back Gallifrey at a later time. They also send a diamond only found on Gallifrey to Earth as a further link, to be found by the Master at the time.
The Doctor lands in London on Christmas Eve, 1851, where he encounters a woman called Rosita Farisi and another man who calls himself ‘The Doctor’. After failing to capture a Cybershade, the two men talk, with the Tenth Doctor believing the other to be a future regeneration. Unfortunately, the other (dubbed ‘the Next Doctor’) is lacking many memories. Meanwhile, the Cybermen are planning an attack with a human ally, Miss Mercy Hartigan. The Tenth Doctor follows the Next Doctor to a house of a dead man, the Reverend Aubrey Fairchild, where they search for clues to what the Cybermen are planning. The Next Doctor begins to regain some of his lost memories; when the Tenth Doctor finds a pair of ‘infostamps’ (the Cybermen’s data storage devices) the Next Doctor remembers he was holding one the night he lost his memory. The Cybermen then attack the house, but before they can kill the ‘Doctors’, the Next Doctor kills them with an electrical discharge from the infostamp.
