The Leisure Hive on the planet Argolis is an entertainment centre for galactic travellers. At the heart of the Hive is the Tachyon Recreation Generator, a machine with a most extraordinary performance capability and vital to the continued existence of the Argolin after their devastating war with the reptilian Foamasi...

While visiting the Hive, the Doctor and Romana are sucked into a whirlpool of treachery and deceit, and are eventually arrested on suspicion of murder. Soon the Doctor is on trial for his life...