Jackie is putting out Christmas decorations and Mickey is working in a garage when they hear the sound of the TARDIS. They meet outside the flats to see the TARDIS crash land and a man stagger out to wish them Merry Christmas - Rose explains that the unconscious figure is the Doctor!

As the Doctor recovers, Rose and Mickey go shopping but are then attacked by Santas . They flee back home and the Doctor dispatches them back from where they came .

Meanwhile a mission to land a probe on Mars has gone horribly wrong and the expedition head Daniel Llewellyn is driven to the Tower of London , where he then finds himself in UNIT headquarters . The probe is actually on a spaceship which is heading to Earth. As it arrives, some people suddenly enter a trance, leaving homes and heading onto roofs . Reports show that this is happening around the world . As things become desperate Harriet Jones (Prime Minister) makes a plea for the Doctor's help .

The Sycorax ship arrives over London and they demand the leader of the planet step forward. Harriet takes on the mantle, and she, Llewellyn and UNIT commander Major Blake are transported to the ship . Meanwhile, in the TARDIS Rose and Mickey inadvertently set of a signal that the Sycorax detect and they beam the TARDIS aboard.

Rose attempts to be a champion for the Earth, but the Sycorax laughter is cut short as the Doctor recovers. He fights the Sycorax leader and it continues outside . The Doctor triumphs and everyone is beamed back to Earth - however, the Sycorax ship is destroyed by Torchwood, and a very angry Doctor brings down Harriet Jones.