Kirk and a landing party are stranded on a planet due to a disease that causes any adult to die a painful death, and must deal with the local children who have survived.

Spock commands a stranded away team when their shuttlecraft is stranded on a planet with hostile natives.

The Enterprise encounters a seemingly peaceful civilization run by a ""benevolent"" being named Landru...who intends for them to join his people.

The Enterprise arrives at a planet to establish diplomatic relations and finds itself in the middle of a "peaceful" war that threatens to destroy the ship.

Kirk and Spock must travel into the past in order to correct a change that will alter history.

The ship travels to Deep Space Station K7 to guard a consignment of grain bound for Sherman's Planet. On arrival, a trader named Cyrano Jones gives Lt. Uhura a tribble, with dramatic consequences. Kirk and the crew also have to deal with the arrival of Captain Koloth and his Klingon battlecruiser, but the tribbles unexpectedly reveal a plot to poison the grain.

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

The Enterprise is in danger when Janice Lester, one of Kirk's former lovers, steals his body.