After answering a call-out to a Tokyo fire, where International Rescue’s assistance was not needed, Scott Tracy is returning to Tracy Island when Thunderbird 1 is suddenly attacked by a squadron of unidentified fighters. Crash-landing in the Sahara Desert, Scott hits his head on his craft’s controls and falls unconscious, his radio smashed. Meanwhile, the lead fighter pilot, dressed in exotic attire with a “Z” symbol on his helmet, reports the successful assault in a strange language. On Tracy Island, Gordon plots Scott’s approximate position so that Virgil, Brains and Tin-Tin can set off in Thunderbird 2 with first-aid equipment.