Arriving on Space Station Nerva in its distant past, the Doctor, Sarah and Harry find its crew threatened by a mysterious plague. Discovering that things are not as they seem, they uncover a Cyberman plot to destroy Voga, planet of gold.
Tom Baker
as Doctor Who
Elisabeth Sladen
as Sarah Jane Smith
Ian Marter
as Harry Sullivan
Ronald Leigh-Hunt
as Commander Stevenson
William Marlowe
as Lester
Kevin Stoney
as Tyrum
David Collings
as Vorus
Alec Wallis
as Warner
Michael Wisher
as Magrik
Christopher Robbie
as Cyber-Leader
Melville Jones
as First Cyberman
Brian Grellis
as Seprah
