SHADO - an acronym for Supreme Headquarters Alien Defence Organization - is located beneath a supposed film studio in the English countryside and run by Commander Straker, who poses as a film producer. When an Unidentified Flying Object attacks a plane in which Straker's deputy Colonel Freeman is travelling it is shot down and investigated. The body of an alien is found and discovered to have transplanted human body parts, seemingly from a trio who disappeared in nearby woods a decade earlier. It is part of the alien plan to take over the Earth to study and imitate humans. Written by don @ minifie-1

Colonel Paul Foster is a test pilot whose aircraft is accidentally caught up in a battle between an Unidentified Flying Object and a SHADO rocket. Foster's plane is shot down and his co-pilot is killed. When he comes round in hospital nobody will believe his fanciful story of what he saw. Until he is made an offer that he cannot refuse, namely an invitation to join SHADO and donate his skills or, quite simply, death. Written by don @ minifie-1

SHADO pilot Jim Reagan is on leave and whilst driving down a country road with his wife at night, he sees a Siamese cat blocking his way. When he gets out to tend to the cat, he is rushed by aliens who abduct him and operate upon him. As a consequence, when he is returned to Earth he is totally under the influence of the cat and its commands - and the cat is at SHADO headquarters. Written by don @ minifie-1

Lunar Module 32 is destroyed when a limpet craft operated by the aliens attaches itself to its side and blows it up. The wreckage is widespread. Straker then orders a clean-up operation to rid the countryside of all craft detritus. However, this is not enough for General James Henderson, the chief of the International Astro-Physical Commission, who believes that SHADO should be disbanded. Written by don @ minifie-1

Straker's son John lives with Straker's ex-wife Mary, who has re-married. Straker is having a day out with the boy, John, but it ends in an argument with Mary and John is run over and seriously hurt. Drugs can be obtained to save him in America and a SHADO craft is sent to fetch them. However, Straker gets an alert call to say that an alien defector which could do untold damage to Earth is in the range of the SHADO craft. SHADO can destroy the alien but it means diverting the means to save John. Written by don @ minifie-1

John Croxley is a man with Extra Sensory Perception, which enables him to read the minds of other people, although he regards it as a curse and has sought medical aid. One day, following a dog-fight with a UFO craft, The UFO crashes into and destroys Croxley's house, at the same time causing the death of Croxley's wife. Holding Foster responsible for his bereavement, Croxley uses his powers to read Foster's mind and find out all about SHADO, which he intends to destroy. Written by don @ minifie-1

Paul Foster and his co-pilot Frank Craig are attacked by a UFO which infiltrates their minds and hypnotises them into wanting to kill Straker. Straker actually saves their lives when their craft is about to be destroyed, but, on their return to SHADO, Craig makes an attempt on Straker's life whilst Foster seeks to discredit him. Written by don @ minifie-1