In 1986 a new planet appears in the Solar System which turns out to be a long-lost twin of Earth's named Mondas. Its inhabitants are the Cybermen.
Quest roles:
William Hartnell(The Doctor), Anneke Wills(Polly), Michael Craze(Ben), Earl Cameron(Williams), Robert Beatty(General Cutler), Dudley Jones(Dyson), David Dodimead(Barclay), Alan White(Schultz), John Brandon(American Sergeant), Steve Plytas(Wigner), Christopher Matthews(Radar Technician), Shane Shelton(Tito)