Late December, 1999: the brink of a new millennium. An anachronistic British Police Box materialises in San Francisco's Chinatown amid a hail of bullets which find an unintentional target — a strange man who walks out of the Police Box. Despite the best efforts of Dr Grace Holloway, the unknown traveller dies and his body vanishes. And soon another stranger appears, claiming to be the same man inside a different body; a mysterious wanderer in time and space known only as the Doctor.

But the Doctor is not the only time-traveller in San Francisco. His oldest adversary, the Master, is there as well, desperately trying to steal the Doctor's newly-regenerated body. Before long, the Doctor is faced with a choice: to save his own life, or the billions of people who have no future unless the Master is stopped. If only the Doctor could remember how...