When the Doctor and the recently regenerated Romana arrive on a radioactive planet, the Time Lord has the strangest feeling that he has been there before. Exploring the ruins of an old city, it is not long before they discover the disturbing truth. The TARDIS has materialised on Skaro - original home to the evil Daleks. But who are the mysterious Movellans and what terrible treasure are the Daleks seeking? The answer lies deep beneath the city...