The
USS Enterprise arrives at a planet in the Omicron Delta system. Scans reveal the planet is congenial, but that there is no animal or insect life of any sort. The crew is exhausted after three months of operations, so
Captain Kirk announces
shore leave for off-duty personnel, but first he orders survey parties to scout the planet.
Dr. McCoy and
Lt. Sulu form one survey party. They find a truly beautiful and peaceful planet. McCoy calls Kirk to report that he had just seen an anthropomorphic
white rabbit, and that a moment later
Alice, from
Alice in Wonderland, appeared and asked McCoy if a rabbit had passed by. Kirk disbelieves this, thinking that McCoy is trying to get Kirk to also take shore leave, which Kirk had said that he didn't need. Science Officer
Spock persuades Kirk to beam down by pointing out that his physical fitness report shows that his performance has deteriorated. After Kirk and his yeoman, Tonia Barrows, beam down, McCoy shows Kirk the tracks of a large rabbit. Elsewhere, Sulu finds and fires a
Colt Police Positive revolver. Then Yeoman Barrows reports that she was attacked by
Don Juan; her uniform is torn. Kirk is briefly accosted by Finnegan, a cocky practical joker who tormented Kirk during his Academy days, and meets Ruth, a former girlfriend. Sulu is attacked by a
katana-wielding
samurai, and he reports that his phaser didn't work. Kirk also finds that his phaser isn't working. Kirk orders a halt to the shore leave before any personnel have been beamed down. Spock reports that the planet is emanating a force field that is drawing energy from the ship's engines and disrupting communications. The energy patterns suggest industrial activity. Spock beams down to gather sensor readings as communications between the ship and planet degrade, stranding Spock with Kirk and the survey parties on the planet with no means of communicating with the ship. After McCoy asks Yeoman Barrows to change into a medieval dress, a
knight on horseback charges them. McCoy protects her but is impaled by the lance and killed. Kirk shoots the knight with Sulu's revolver. Kirk and Spock analyze the knight's body; it is composed of the same material as the planet's vegetation. A
World War II fighter plane strafes the landing party; during the commotion, the bodies of Dr. McCoy and the knight vanish. Spock asks Kirk what was on his mind before his "vision" of Finnegan. Kirk says he was thinking of his academy days. As Spock expects, Finnegan reappears. Finnegan taunts the Captain before running off, with Kirk chasing him. They have a fistfight and Kirk knocks out Finnegan, which Kirk says that he has always wanted to do. Spock and Kirk realize that their thoughts are causing their fantastic experiences, but also that the experiences are increasingly deadly. Kirk orders everyone to stop thinking, about anything. An elderly man appears: the "Caretaker", who explains that "[t]he planet is an '
amusement park'"; its constructs are not intended to be harmful or permanent. Accompanying him is Dr. McCoy, revived by the planet. McCoy shows off the two Rigelian cabaret girls he thought of after being revived. The Caretaker apologizes for the misunderstandings and offers the planet's services to the ''Enterprise's'' crew, cautioning that they must choose their amusements carefully. Kirk accepts the offer as Ruth reappears, and authorizes the crew to beam down. ==Production==