A strange young man is dropped off on the Enterprise. At first, he is just rude and childish. As time goes along, he begins to alienate the crew. The ship that left him off is destroyed. Signs are pointing to this kid having something to do with these things. As things play out, he becomes more and more impatient and reactionary. When laughed at during judo training, he makes his teacher disappear. He terrorizes the crew and needs to be controlled. Robert Walker, Jr. is startlingly spooky as Charlie. If one wants to find a bit of a comparison, think of the Twilight Zone episode where the little boy can send people off to a cornfield. People begin to speak to him differently because they are frightened. The use of creatures who know no bounds creates issues. The petulance of this person makes him ten times more terrifying. While it's an interesting episode, it depends on forces beyond the scope of the crew and the ship.