After an abortive escape attempt, the Doctor is strapped down to a Dalek mind analysis device, where images of the two previous Doctors are shown to confirm to the Daleks that he is, indeed, their sworn enemy. The Controller bursts in, saying that using the mind analysis device will kill the Doctor. He then says that they should keep the Doctor alive for information on the rebels, and that he will question the Doctor personally. The Daleks gloat to the Doctor that they have discovered time travel, invaded Earth again, and changed the course of history. The Controller explains that at the end of the 20th century, 100 years of devastating worldwide wars began, killing 7/8ths of the population and forcing the rest to live in little more than holes in the ground. It was during this period that the Daleks invaded, conquering the world and using it for raw materials to fuel the expansion of their empire.