The Doctor faces the end of his life as the Master's plans hurtle out of control. With the sound of drums growing louder, and an ancient trap closing around the Earth, the Doctor and Wilf must fight alone. But sacrifices must be made, and the deadly prophecy warns: "He will knock four times."With almost everyone on Earth now recast in his image, The Master controls the world. He's shocked however when he realizes that one person hasn't changed. The Doctor soon realizes that the...