XL5 transports Geologist Frazer to Electron for a survey. When Frazer discovers a strange rock in a deserted town, he goes mad and threatens to destroy Fireball Junior, if Steve doesn't take the rocks back to Earth.
Alan Fennell
Writer
John Kelly
Director
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)