In the third episode of the four-part story "The Moonbase," the Doctor (
Patrick Troughton) is now fully aware that the Cybermen intend to destroy the earth by spreading deadly disease. Armed with this knowledge, the Doctor does his darnedest to stop the Cybermen from taking over the moonbase, which controls the Earth's weather. Written by Kit Pedler and (uncredited) Gerry Davis, "The Moonbase, Episode 3" was originally broadcast on February 25, 1967; this episode apparently no longer exists. ~ Hal Erickson, All Movie Guide