With the threat of interplanetary war looming, the human race prepare for the end, little knowing their enemies lie at the heart of the British government. As the Ninth Doctor, Rose Tyler and new friend Harriet Jones battle for their lives in 10 Downing Street, the Slitheen family set their plans for the destruction of Earth into motion. With the world changing around him, the Doctor is powerless, and it seems only Mickey Smith can save the world...