The scientific colon on Triacus sends a distress signal and the Enterprise
goes to investigate. Kirk, Spock, and McCoy beam down and find members of the colony scattered around the area, dead. They find Professor Starnes, the colony leader, who dies even as they find him. McCoy checks and determines that they all took cyalodin, a deadly poison. They play back Starnes' tricorder and hear his log warning that they're being threatened by an enemy within. To stop it, they vow to destroy themselves. Suddenly the colony survivors arrive: five children. They greet the landing party and then start playing around their parents' corpses.
As the Enterprise
landing party bury the adults, the children put up with the ceremony briefly and then start playing again. McCoy warns that he can't account for the lack of grief and warns that questioning them could damage their psyches. As Kirk has the children beam up with McCoy, he and Spock explore the area. They discuss whether the suicides were somehow induced and if the person responsible spared the children for a reason. Spock picks up a signal coming from a nearby cave. They go in and Kirk is suddenly overwhelmed by strong feelings of anxiety. They can't account for his feelings and they die away as he leaves the cave.
Aboard the ship, Nurse Chapel entertains the children while McCoy warns that he's been unable to learn anything from testing the children. Kirk talks to the children who seem unconcerned about their parents. When Tommy, Professor Starnes' son, asks for more ice cream, Kirk says they can't and the children accuse him of acting just like the colony adults. Kirk talks to Tommy privately and asks what happened on the planet. Tommy says that his father was upset but that was normal for him and the others. He claims that the parents now have the planet to themselves and they'll be happy without the children. As Tommy follows after the others, Kirk orders ship's security to watch the children.
Later, the children chant and call upon the "Friendly Angel." A golden angelic figure appears in the cabin and says that they've done well. It tells them that they must find more friends on Marcos 12, a Federation settlement, but Kirk will try to stop them. The alien, Gorgan, says they must kill anyone that gets in their way but soon they will have a million friends to play with and take over the galaxy.
On the bridge, Kirk and Spock review Starnes' log tapes on the science station monitor. Over the course of the log entries, Starnes becomes increasingly uneasy and says that the other parents have similar feelings. The professor talks of how they found a cave where one survivor of the planet's civilization took refuge. As he starts to go into more detail, Tommy visits the bridge. He makes a pounding gesture with his fist and the monitor shuts down. Tommy asks if they can go to see his relatives on Marcos 12 but Kirk informs them that the planet isn't within their scheduled sector. While Kirk goes to his quarters with Spock and McCoy to review Starnes' log tapes, Tommy makes the same gestures. He takes control of Sulu and Chekov and has them set course for Marcos 12, unaware that they're doing anything wrong. When Uhura notices, she tries to alert them that they've left orbit but Tommy takes control of her as well.
Scotty is visiting Auxiliary Control and notices that the ship has left orbit. He tries to convince one of the crewmen they've been deceived, but he's under the control of another child. Scotty tries to subdue the man but is rendered unconscious.
Kirk, Spock, and McCoy watch the remainder of Starnes' tapes. The professor says that his mind was influenced and he found himself contacting Starfleet for a starship, only to realize he had no idea what he was doing. Spock checks the records and reports that thousands of years ago a race of marauders went through the system but was stopped at Triacus. According to the legends, the evil slept but waited for the day when something would set it in motion once more. Kirk believes that the evil is at large once more and the children are the catalyst, but McCoy warns that if the children's grief isn't handled properly, it could traumatize them. Kirk isn't willing to let preserve the children at the cost of the crew's lives.
Kirk and Spock accompany a relief team of two security guards to the bridge. They beam down the two men and then try to beam up the original team, only to realize they can't get a transporter lock. Kirk and Spock check the monitors and realize that they're no longer in orbit above Triacus, and sent the two security guards to their deaths.
On the bridge, Kirk and Spock find the mesmerized crew satisfied that nothing has changed. The children chant, summoning Gorgan once more. He tells the children that the enemy has found them out and that they must summon the "beast" that lies within each person's heart to destroy them from within.
As Gorgan disappears, Kirk orders Sulu to change course. Tommy makes the helmsman see a tunnel of knives that will kill them if they get off course and Sulu refuses to endanger the ship. Kirk tries to get Uhura to contact Starfleet but she suffers a hallucination that she's dying of disease and old age and is paralyzed with fear. Under Tommy's influence, Spock doesn't notice anything unusual and Kirk's orders to security become scrambled. When Kirk threatens Tommy, the boy causes him to suffer an overwhelming fear of his loss of command, and Spock gets him off the bridge. In the turbolift, Spock assures the captain that he's in control and Kirk manages to overcome his fear and revert to normal.
Heading for Auxiliary Control, Kirk and Spock discover that Scotty is under the children's influence. He refuses to endanger the ship by making any kind of change and tells them to leave before he kills them. Spock notes that to stop the children, they may have no choice but to kill them, even if they're innocent pawns. Before they can decide, Chekov arrives with a security team as Tommy leads them from the background. Chekov orders Kirk and Spock to surrender or he'll kill them. The senior officers fight back and subdue the security team and Tommy runs off in fear.
While Spock locks up the security crew, Kirk goes to the bridge to confront Tommy and the other children. He tells them that Gorgan is a coward and dares him to show himself. As the children refuse, Spock returns to the bridge and plays back a recording of their earlier chant. Gorgan appears and boasts that it's too late to stop him. He notes that Kirk is too weak and that whatever strength he has is cancelled out by his gentleness. In response, Kirk has Spock playback Starnes' logs, particularly the scenes of the children happily playing with their parents. Spock then switches to shots of the parents, dead. Gorgan tries to rally the children but they start crying as their grief comes through. Gorgan begins to decay before their eyes as his true visage is revealed. Without the children's belief, Gorgan is powerless. He disappears as McCoy arrives on the bridge and is pleased to see that the children are expressing their grief normally. The crew reverts to normal and Kirk orders them back on course to the starbase. Share this article with your friends