Very good episode, involving the crew picking up a teenager that has survived alone on a planet that he shouldnt have been able to, and trying to teach him how to interact with others. During the course of the journey it becomes obvious he has powerful psychic abilities, and is as unstable as any teenager…

Very enjoyable, with the lovesick Charlie mooning about after Yoeman Rand, and then getting more and more frustrated with everyone and doing odd assorted things to people (he turns a girl into an iguana, or makes people’s faces turn into a formless, empty piece of flesh). He doesn’t kill any red shirts though (though he makes a guy in a red judo suit disintegrate into thin air). We also get Uhura singing a song making fun of Spock whilst he plays a harp, and Kirk, topless and wearing red tights in the weirdest gymnasium I’ve ever seen.

This story structure (a powerful being having psychic control over the enterprise, ending with a very, very well-known twist that everyone knows from Star Trek) was used several times in the original series, with Charlie X and The Squire of Gothos being the most well-known examples of this particular story.

Very enjoyable episode. To put it in our list of best first

1. Charlie X
2. The Man Trap