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.
An Enterprise landing party finds a planet biologically paradise-like, but soon a crew member is killed by something lurking around. An unidentified, irresistible force from the planet keeps the ship caught and blocks the transporters function. Suddenly a sort of spore eruption knocks Spock out, but only temporarily. They find a primitive village near the power source, devoted to the service of a certain Vall they seem to consider their divine creator; McCoy finds them completely free of disease, aging and natural dangers. They observe them sacrificing food to a temple, apparently housing the machine, which blocks out all other life forms, and instructs the villagers to learn to knock the intruders on the head with lethal force. Their plan is to attack it when in need of another feed.
Primitive inhabitants of Gamma Trianguli VI worship a God who orders them to kill visitors, from the Enterprise.
- Beware of false gods, especially snake shaped ones. Kirk beams down to a planet along with Chekov and a lovely Yeoman named Martha Landon, who is blond and dressed in a red uniform with black tights and Spock and four redshirts, good friends of Kirk.
The planet is like a paradise, but Wait, there are booby traps everywhere. Redshirts are getting zapped left and right, and Spock too, but he is strong enough to survive.
They meet Akuta who has an antenna in his neck, to hear Vaal, the god of the planet. Vaal tells Akuta when it is hungry, then Akuta's people bring Vaal energy food as an offering.
Look Out! Vaal is not happy that the Enterprise is there. Two of Akuta's people, a blond man and woman, see Chekov and Yeoman Landon kissing, and they like it and try it. Vaal is displeased. Now Vaal is crippling the enterprise. They must keep Akuta's people from feeding Vaal, at all costs.
Then Kirk turns the Ship's phasers on Vaal until it is dead. It was not really a god, just a machine. Akuta's people are happy now because they can kiss and make children. Even Akuta accepts the new way of life. "Man was not meant to live in Eden, Mr Spock." says Kirk. Wow.