The Doctor and Romana visit the Leisure Hive on the planet Argolis, the surface of which is uninhabitable following a twenty minute nuclear war between the Argolins and their enemies the Foamasi. The Argolins themselves are now sterile. Pangol, the youngest, was created by the Tachyon Recreation Generator, a machine that runs games in the Hive.

He now secretly plans to use the Generator, modified by an Earth scientist named Hardin, to recreate himself many times over, forming an army of duplicates to destroy the Foamasi. Pangol's mother Mena, the controller of the Hive, is meanwhile coming under pressure from a supposedly human financier, Brock, to sell it to the Foamasi.

Foamasi agents from their planet's government arrive and expose Brock and his assistant Klout as members of a renegade Foamasi group called the West Lodge. The Doctor then reconfigures the Generator equipment using components from the randomiser device previously linked to the TARDIS's navigation circuits, and Pangol's plan is foiled as he rejuvenates into a babe in arms.