The hugely powerful Key to Time has been split into six segments, all of which have been disguised and hidden throughout time and space. But when they arrive at exactly the right point in space, they find themselves on exactly the wrong planet - Zanak. Ruled by the mysterious 'Captain', Zanak is a happy and prosperous planet.
The classic "Doctor Who" adventure by Douglas Adams, this is one of the most popular "Doctor Who" adventures of the Tom Baker era.