When the Doctor accepts an invitation to an audience with a popular horror writer, he's expecting a rather dull evening. But he quickly senses the presence of another Gallifreyan nearby. The Time Lords have a mission for him.

Soon the Doctor and Jo and themselves at the height of the Second World War in 1943. Caught up in a struggle involving occultist Nazis, the Prime Minister, top secret agencies and a mysteriously powerful amulet, they must distinguish friend from foe and avoid sacrifice upon the altar of evil.