The body of an Alien, recovered after a UFO attack on Moonbase, reveals some startling new evidence which overturns all SHADO's previous theories about the Aliens. For Interceptor pilot Jim Regan, the news has tragic consequences as he becomes possessed by the mind of an Alien held in the body of a Siamese cat!

After a UFO inexplicably destroys itself less than two miles from Moonbase, a mysterious crystal rock is recovered, and it causes the person in its vicinity to hallucinate. The man on Moonbase who found it thinks Mexican bandits have taken over Moonbase. It gets transferred to Straker's office, and he hallucinates that SHADO is simply a set for a TV series, he is an actor named Mr. Burns, Moonbase can be reached by stepping through two doors from the main control room at SHADO HQ, and "Mr. Straker" is not available. Straker breaks the hallucination by jumping in on the scene while the "character" Gen. Henderson is doing a close-up of the line they were doing when the hallucination began.