Star Trek: The Original Series, Series 1, Episode 25.
First broadcast on Thursday 9 March 1967

A terrifying cave monster attacks a bunch of miners in pastel jumpsuits and burns them alive: it must be killed to ensure a continuing supply of raw materials for the engines of capitalism. But then, of course, we reach out, learn that the monster is a person, and thereby discover a terrifying truth about ourselves. A triumph: literally the thing that Star Trek is for.