Trelane
William Campbell

Lt. Karl Jaeger
Richard Carlyle

Lt. Vincent DeSalle
Michael Barrier

Yeoman Teresa Ross
Venita Wolfe

Voice of Trelane's father
James Doohan

Voice of Trelane's mother
Barbara Babcock

During their travels the crew of the Enterprise find a previously uncharted planet directly in their path. Before they can take evasive action Kirk and Sulu vanish from the bridge. Sensor readings indicate that the planet is not capable of supporting human life but a bizarre message in old English received by Uhura persuades Spock to send a landing party down anyway.

On materialising they come across a large, extremely old-fashioned house in which, on entering, they find Kirk and Sulu in a statue-like condition. A man in period clothes appears, introducing himself as Squire Trelane, and releases them from their 'frozen' state. He goes on to explain that he couldn't resist the opportunity to meet real people from his favourite planet and that he has the ability to control matter, which accounts for the breathable atmosphere in the area.

Kirk refuses to play and, to Trelane's annoyance, attempts to leave but immediately finds himself in the choking, poisonous atmosphere of the planet outside the being's control. The experience is brief but compelling. Spock manages to beam the landing party back aboard the Enterprise but Trelane is not going to have his fun spoiled so easily.

He appears on board the Enterprise and transports several members of the bridge crew back to the planet. He is particularly 'taken' by the ladies, but not by their uniforms, which he transforms into exotic ball gowns. He provides a large banquet for them, but the food and drink is completely tasteless and the nearby fire produces no heat. This leads Spock to conclude that the being has been observing Earth as it was centuries ago and that, although Trelane knows about appearances, he has no concept of substance.

As Trelane dances with the women Kirk and Spock notice that he never strays far from a large, ornate mirror. To test his theory, Kirk feigns jealousy at his attentions to the women and challenges him to a duel. Trelane is delighted and allows Kirk to fire a pistol at him but, instead of aiming it at Trelane, he destroys the mirror, revealing some kind of mechanism. The Squire is furious as their surroundings disappear and they transport back to the Enterprise.

Kirk immediately tries to leave the vicinity of the planet but it follows their every change of course. Kirk beams back down to face Trelane but finds himself in a courtroom with Trelane as the judge and ready to hang him. Kirk saves himself by proposing a more interesting method of getting rid of him. Trelane agrees to the idea of a 'hunt' which immediately gets underway. Things look bad for Kirk as Trelane insists on using his powers unfairly to gain an advantage and soon has him trapped, at his mercy.

At that point two disembodied voices call to Trelane telling him to stop playing and come in. The 'Squire of Gothos' turns out to be nothing more than an extremely powerful 'naughty little boy'. His parents make their apologies to Kirk for allowing Trelane to play with such a vulnerable species and the 'Squire of Gothos' disappears, complaining that they never let him have any fun. They maintain the environment until a bemused landing party, free to leave now, returns to the Enterprise.