The Doctor is returning home to Gallifrey with the remains of his arch-nemesis, the Master. Forced off course, the TARDIS arrives in San Francisco on New Year's Eve 1999, where the Doctor is critically wounded in a gangland gun battle. At the local hospital, Dr Grace Holloway fights - and fails - to save his life. Later, in the morgue, the Doctor wakes up a new man. But he is not the only one - the Master has also found himself a new body. As the clock counts down to the start of the new millennium, can the Doctor stop his oldest enemy destroying all life on Earth?
