Straker must face his claustrophobia when the Skydiver submarine is damaged and unable to surface.

While investigating the disappearance of a probe, Troy and Phones are captured by the survivors of a ruined subterranean city.

A millionaire's young daughter is targeted by rivals who want to block a company take-over. He hires the Protectors to shelter her, which they must do so without raising her suspicions.

Criminal masterminds uncover the McClaines' involvement with WIN and kidnap Mac for further information.

A gang of criminals masquerade as International Rescue to conceal their theft of top-secret military plans. The ensuing worldwide manhunt for International Rescue leaves the organisation powerless to operate in a rescue situation until its name is vindicated, just as a member of a manned reconnaissance satellite is suddenly trapped in space while trying to repair the station.

Spectrum mounts an raid on the headquarters of Vulcan Industries. Colonel White confronts the board of governors over their recent breach of the Martian Exclusion Directive: despite the fact that the company's durinium mining operation on Syrtis Major was suspended some time ago, a three-man maintenance team recently left for Mars. On learning that all contact with these engineers has since been lost, Colonel White sends Captain Scarlet, Captain Blue, Captain Ochre, Destiny Angel and Doctor Gold to investigate.

Koenig and a colleague land on an Earth-like planet, once populated but now devoid of life, they flee when a man steps from a transport booth and dies. They fly the Eagle to the planet's companion body and crash, the colleague is killed by a forcefield and Koenig is captured. Taken to a penal colony on the planet's moon, he becomes the person of interest to the warden who then conceals Koenig's survival when other Alphans arrive in search of the Eagle crew.

Zelda lures the Terrahawks to Jupiter's moon Callisto by ransacking a listening post there. Once they arrive, they find themselves being stalked by the fearsome Sporilla.

A man with E.S.P. knowledge of SHADO is co-opted by the aliens.

Mitch switches places with a musical gorilla.