 The Time Ring returns The Doctor, Sarah and Harry to Nerva Beacon thousands of years before they left. Where the Doctor, Sarah and Harry find the Beacon s crew have been wiped out by a space plague, only to discover the crew have been murdered by a cybermat and the culprits are the Cybermen and geologist Professor Kellman who bid to wipe out "Voga" a planet of gold, home of the subterranean Vogans who defeated the Cybermen in a war.