A mysterious plague strikes Space Beacon Nerva, killing its victims within minutes. When Doctor Who lands, only four humans remain alive. One of these seems to be in league with the nearby planet of gold, Voga... Or is he in fact working for the dreaded Cybermen, who are now determined to finally destroy their old enemies, the Vogans? The Doctor, Sarah and Harry find themselves caught in the midst of a terrifying struggle to the death - between the ruthless, power-hungry Cybermen and the desperate determined Vogans.