On a planet populated by children whose aging process has been slowed artificially. Kirk’s landing party members contract a virus that kills adults. Despite their violent attacks, Kirk is determined to help the children.

When a wild eyed maniac escaping from the Tantalus Penal Colony turns out to be one of the psychiatric staff, Kirk investigates the institution and discovers a chilling exercise in mind control.

Despite the earlier Romulan war, the Romulans have never been seen in person. The Enterprise, in pursuit of a Romulan aggressor, makes a discovery that causes suspicion about a senior crew member.

The crew of the Enterprise tracks down a Federation observer on a planet dominated by a "Naziesque" regime.

Captain Kirk must find the cure to a deadly disease and put an end to another Starfleet captain's cultural interference.

Having been found trespassers into Melkotian space, Captain Kirk and his companions are sent to die in a re-enactment of the gunfight at the O.K. Corral.