Kirk and a landing party beam down to what seems to be an ideal, Eden-like planet. They soon find however that the planet is ruled by a powerful computer that keeps its local inhabitants - primitive and simple tribesmen - happy and healthy. With the Enterprise locked in a tractor beam and slowly being dragged into the planet's atmosphere, Kirk and Spock must find a way to disable the computer. Realizing the threat to its existence, the computer orders the tribesmen to kill the visitors.