Aliens plan to infiltrate SHADO headquarters from a base under the ocean.
Straker reminisces about the formation of SHADO in the 1970s, and how his duties as commander led to his failed marriage.
Straker and Freeman race to prove Foster innocent after he is tried and sentenced to death for the sale of military secrets.
A woman just-wakened from a 10-year coma induced by hallucinogens tells Straker she alone knows where aliens placed a bomb.
Straker notes strange behavior and odd incidents after a woman reporter assigned to interview him arrives at headquarters.
A human traitor interferes with Straker's attempts to rescue SHADO headquarters from an alien-induced state of suspended animation.
SHADO blames a private business firm's geological scanner for the disruption of visual and audio transmissions from the moon.
Straker struggles to free the mind of a friend found on a Pacific island after inexplicably vanishing with his spaceship.
SHADO crews rescue Foster (Michael Billington) from a saucer, but learn he now must breathe an alien liquid to survive.
Traitors blackmail a loyal Moonbase operative into cooperating with them by threatening to murder his wife if he does not.
After a UFO explodes near Moonbase, people who touch the debris experience hallucinations bringing death to them and their friends.
Injured Foster must cooperate with an invader to reach the installation alive after an alien vessel incapacitates his Moonmobile.
Three extraordinarily strong people under alien control destroy secret SHADO bases and threaten to annihilate headquarters.
SHADO places a powerful electron telescope inside an orbiting spaceship and circles the alien planet to spy upon its inhabitants.
Interceptors fail to halt a UFO's progress toward Earth.
Straker investigates a woman working for naval authorities after learning of a naval gunship's shooting down of a UFO at sea.
SHADO appears helpless to rescue Straker and his crew from a submarine disabled at the bottom of the ocean in an alien ambush.
Straker intervenes when a woman and her lover kill an alien mistaken for her husband, then plot again to kill her spouse.
Straker must choose between risking everyone's life to save his young son, or stopping a downed alien spacecraft.
SHADO mobile units search the countryside to find an alien saucer responsible for one man's death and another's capture.
Straker and Freeman investigate when a UFO smashes into a home, killing the wife of a man who can read minds and predict the future.
Foster risks his life and reputation to prove the abundant debris orbiting Earth creates potentially deadly threats to friendly vessels.
Aliens land secretly on Earth, hold SHADO pilot Regan's wife hostage, and place him under a hypnotic spell to obey them.
Straker tries to cure Craig and Foster of a hypnotic urge to murder him induced by aliens who followed their craft to Earth.
Straker (Ed Bishop) commissions civilian test pilot Paul Foster (Michael Billington) to join SHADO as a colonel in the organization.
SHADO mobilizes to combat an alien invasion.