The XL5 becomes caught in the gravitational pull of planet Megneton and discovers the plot by the Solars to bring the Earth's moon into their orbit.
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)
Guest Star