The Enterprise crew discovers that the ship cannot escape orbit of a planet that doesn't even exist on the star charts. Kirk and a landing party beam down to the surface of the mysterious planet and their captor is revealed to be the immature but powerful Trelane, who initially seems to be a student of ancient Earth history (as demonstrated by his 17th century mansion, clothes and furnishings). Kirk, discovering that Trelane's hold on the Enterprise comes from a power far beyond 23rd century technology, must try to beat Trelane at his own game, but Trelane rewrites the rules constantly to make sure he's winning.
