Donna is about to marry her boyfriend Lance on Christmas Eve, but she finds herself transported aboard the Tardis. As the Doctor tries to get Donna to the church on time, the alien Empress of Racnoss watches closely from the throne in her spaceship. Somehow Donna is the key to an ancient plot to destroy the Earth. With time running out, can the Doctor solve the puzzle, defeat the Empress and stop her army of robot Santas?
