The Magellanic Clouds, the planet Ribos, an unknown time. Ordered by the White Guardian to collect the pieces of the omnipotent Key to Time, The Doctor, K-9 and his new assistant Romana arrive. Collecting the first segment is not going to be easy…

Trying to obtain the first segment of the Key to Time, the Doctor and Romana are swept up in an elaborate con. The target – the homicidal Graff Vynda K.