Nerva is a station acting as a beacon warning space traffic of the existence of Voga, a new asteroid abundant in gold, orbiting Jupiter. The Doctor, Sarah and Harry arrive and learn that a space plague has killed all but a handful of Nerva's crew. A scientist named Kellman is a traitor working with a group of the Doctor's old adversaries the Cybermen, who want to destroy Voga as gold is toxic to them, and the 'plague' is the result of poison injected into its victims by Cybermats......., but that's enough plot from this omnibus edition of one of the classic four episodes long Doctor Who series from the fabled Tom Baker era.