Gerry and Sylvia Anderson have gifted the world of TV sci-fi with many iconic series: Space: 1999, Thunderbirds and Stingray, to name a few. Most of their creations were performed by marionettes but UFO was the first live action series from the Andersons.

Action was set in the near future when the human race faced a sinister alien plot to secretly harvest organs from the unsuspecting Earth populace. The aliens arrived in Earth's orbit from their far away planet but could only survive a few days in our atmosphere before exploding. It was much better for them to be submerged underwater where they operated a secret alien base.

An organization name SHADO (Supreme Headquarters Alien Defence Organisation) was established to fight against the alien invaders. Using a movie studio as cover, Commander Ed Straker, U.S. astronaut, headed the covert outfit which included a large number of military officers. The series had a sizable ensemble cast that came and went throughout the show's run. Other than Straker, regular characters included Lt. Gay Ellis, Col. Alec Freeman, Col. Paul Foster, Gen. Henderson and Dr. Doug Jackson. When not on Earth headquarters, the characters appeared on Moonbase, Earth's forward line of defence, located on the moon (duh).

The alien race was never named but they were humanoid in appearance. They wore space suits with large helmets that contained a green liquid (ostensibly to cushion their melons from the high speeds of interstellar travel) and used white contact lenses in their eyes with small pinholes for seeing.

Though the series had complex backstories and plot arcs and featured some truly outstanding special effects, broadcasters didn't really market it to audiences because they couldn't decide whether it was an adult or a kids show. UFO was cancelled after 26 episodes but the Andersons returned a few years later with the more successful Space: 1999.