UFO: Identified (Episode 1)

SHADO - an acronym for Supreme Headquarters Alien Defence Organization - is located beneath a supposed film studio in the English countryside and run by Commander Straker, who poses as a film producer. When an Unidentified Flying Object attacks a plane in which Straker's deputy Colonel Freeman is travelling it is shot down and investigated. The body of an alien is found and discovered to have transplanted human body parts, seemingly from a trio who disappeared in nearby woods a decade earlier. It is part of the alien plan to take over the Earth to study and imitate humans.