The Invisible Enemy first aired October 31, 1964 as episode 7 in season 2 of The Outer Limits (1963 TV series). It was directed by Byron Haskin, starring Adam West.


The first manned expedition to Mars finds itself being killed one by one by an alien predator.


The episode is based on a short story by Jerry Sohl, 'The Invisible Enemy', first published in Imaginative Tales magazine in September 1955.