Captain Kirk, Dr. McCoy, and First Officer Spock beam down in time to witness the death of Professor Starnes, the leader of a scientific expedition team.
The crew bring the children back to the Enterprise, where McCoy evaluates them and determines that they are suffering from lacunar amnesia, unaware of what happened to their parents and unable to grieve.
He advises them to take control of the crew in order to get to Marcus XII, his preferred destination, where he will dominate millions more followers and conquer the galaxy.
The eldest child, Tommy, uses mental powers Gorgan has bestowed on the children to trick the crew into steering the ship while presenting illusions that make them think they are still in orbit above Triacus.
Upon reviewing a troubling expedition film recorded by Starnes, Spock, McCoy, and Kirk return to the bridge to find the children and Gorgan fully in control of the crew through illusion and fear.
Unable to break their hold on the crew, Spock observes that the children are merely possessed by Gorgan, who must be the evil embodiment of an ancient group of space-warring marauders released by Starnes's archaeological survey.
[3] During a climactic scene on the bridge, the oldest child, Tommy Starnes (played by Craig Hundley), casts a spell to make Captain Kirk's voice unintelligible, so as to render him unable to give orders to his crew.
[6] While the general fan consensus was that this was one of the poorer third-season episodes, and that Captain Kirk's "brusque, exaggeratedly authoritarian and at times unmistakably hostile attitude" towards the titular children undermined both the moral and the plot, Richard Keller of TV Squad listed Gorgan as the tenth scariest television character.
[12] This episode was released in Japan on December 21, 1993, as part of the complete season 3 LaserDisc set, Star Trek: Original Series log.3.