On a colony in outer space, a crazed mutant crew member (Warren Oates) controls everyone with his incredible psychic powers. He can read their thoughts and kill with a single thought! And, when an investigator is sent from Earth, he is in danger, as the all-power (and VERY bug-eyed) mutant is not about to let him return home with knowledge that the colony is being terrorized!
Rixrex is correct, the plot for "The Mutant" is clearly reworked in the second "Star Trek" pilot, "Where No Man Has Gone Before". Both involve a normal guy becoming a mutant--a seemingly all-powerful and completely amoral mutant who scares the crap out of the rest of the folks! And, in both cases, there clearly is a need to stop this mutant--lest everyone die when they happen to displease him...and they are surely eventually going to do this! And, now that I think about it, they both are variations on the "Twilight Zone" episode "It's a Good Life"--where an evil child controls everyone--lest he wish them out of existence or worse! This is NOT a bad thing, as the evil mutant idea produced some great episodes of these series--as these three are among the best. It also was used, with a few variations, in the magnificent "Village of the Damned". So why did this work so well? The idea of people becoming vicious all-powerful monsters is so compelling--as it explores the basest instincts within all of us. Heck, using the reasoning in these shows, even Mother Theresa would have become an animal depending on her circumstances. Well worth seeing--well-written and suspenseful.