In the conclusion of the four-part story "The Moonbase," the Cybermen begin their final assault on the moonbase which controls the Earth's weather in the year 2070 A.D. The Doctor (
Patrick Troughton) must prevent the Cybermen from emerging triumphant, lest the Earth be devastated by germ warfare. Written by Kit Pedler and (uncredited) Gerry Davis, "The Moonbase, Episode 4" was originally broadcast on March 4, 1967; though this episode is presently known to exist, episodes one and three have apparently long since vanished. ~ Hal Erickson, All Movie Guide