Show was about aliens who were visiting the Earth and kidnapping humans. An organization called SHADO was formed to defend us from them. SHADO had several lines of defense. Missiles could be launched from a base on the Moon. High altitude aircraft could attack after being launched from submarines. There were also a fleet of armored vehicles spread out all over the planet. The episodes typically involved attempted alien attacks and how Earth defenses stopped them. The show tane a years break in after the first series in 1970 then made a come back in 1973 but was stoped after just 5 episodes into the second series.