The Doctor's warnings are ignored and the Cybermen take over the base, hampering the crew's efforts to help Zeus IV.
Quest roles:
William Hartnell(The Doctor), Anneke Wills(Polly), Michael Craze(Ben), Earl Cameron(Williams), Roy Skelton(Daleks (voice)), Reg Whitehead(Jarl), Robert Beatty(General Cutler), Dudley Jones(Dyson), David Dodimead(Barclay), Alan White(Schultz), Steve Plytas(Wigner), Christopher Matthews(Radar Technician), Harry Brooks(Krang), Ellen Cullen(Geneva Technician), Glenn Beck(T.V. Announcer), Gregg Palmer(Gern)