UFO Episode 10 “The Square Triangle”

UFO is a 1970 British television science fiction series about an alien invasion of Earth, created by Gerry Anderson and Sylvia Anderson with Reg Hill, and produced by the Andersons Century 21 Productions for ITC Entertainment company. UFO was the Andersons' first totally live-action TV series. Despite the assumption of many TV station executives, the series was not aimed at children but was intended for an older audience; many episodes featured adult themes such as adultery, divorce, and drug use.

The year is 1980. Earth is being visited and attacked by aliens from a dying planet and humans are being covertly harvested for their organs by the aliens. The show's characters are members of a secret, high-technology international agency called SHADO (an acronym for Supreme Headquarters, Alien Defence Organisation) established to defend Earth and humanity against the mysterious aliens and learn more about them, while at the same time keeping the threat of an alien invasion hidden from the public.

SHADO's main headquarters is hidden beneath a film studio near London England. SHADO also has a base on the moon (Moonbase) and a fleet of submarines. Incoming UFO's are initially detected by an Earth orbiting satellite named SID (Space Intruder Detector).

An initial interception attempt is made in space with three Interceptor craft launched from Moonbase. A second attempt is made in the Earth's atmosphere with a fighter plane (Sky One) launched from Skydiver. Landed UFO's are tracked down with ground Mobiles.