Kernak, ruler of Kemple plots the resettlement of his people to Planet Olympus by poisoning Olympus' ruler's son. Venus and Matt are captured and must be rescued by Steve.
Gerry Anderson
Robert the Robot (voice) (uncredited)
David Graham
Lieutenant Ninety (voice)
Sylvia Anderson
Doctor Venus (voice)
Paul Maxwell
Colonel Steve Zodiac (voice)
John Bluthal
Commander Wilbur Zero (voice)