Star Trek: Season 2, Episode 20

2 - 20: Return to Tomorrow

Enterprise responds to odd readings, which lead the crew to a planet similar to Earth, except that it is much older, and a cataclysm stripped its atmosphere away a half million years ago; it has been dead ever since. But from somewhere on that world comes a voice. Something has evidently endured 500,000 years - the last survivors of the civilization that flourished here. And all they want are the bodies of a few humans...