The Squire of Gothos

While crossing a star desert, the Enterprise comes upon an unknown planet, and Kirk and Sulu disappear from the bridge. A landing party finds them held in an elegant castle belonging to Trelane, a self-styled retired general who has studied Earth's past from afar and admires its wars. Bored and all-powerful, he treats the crew as his playthings, staging banquets, dances and duels. Kirk realises that Trelane's power comes from a machine hidden behind a mirror, and smashes it, but the planet keeps reappearing in the ship's path. Kirk beams down alone and offers himself as quarry in a hunt to spare his crew. Just as Trelane is about to kill him, two disembodied voices call Trelane away. They are his parents, and he is only a child. They scold him, apologise to Kirk and let the Enterprise go.