Whilst returning the Master's remains to their home planet of Gallifrey, the Doctor crash lands the TARDIS on Earth in San Francisco in the year 1999. Gunned down by a street gang, the Doctor is rushed to hospital, where exploratory surgery by Dr Grace Holloway triggers a regeneration into the Eighth Doctor. Meanwhile, the Master has taken over the body of a paramedic and infiltrated the TARDIS, which he plans to use in his latest scheme to take over the Doctor's new body and destroy the world.