Strange radiation exposes the command crew of the Enterprise to the effects of rapid aging.

The crew of the Enterprise encounters an energy-draining field which may be able to destroy the galaxy.

The crew of the Enterprise discovers Klingon interference in the development of a formerly peaceful planet and is forced to help maintain a balance of power.

Ancient alien minds are given control of Captain Kirk's and First Officer Spock's bodies.

While back in time observing Earth in 1968, the Enterprise crew encounters the mysterious Gary Seven who has his own agenda on the planet.

On a distant planet, Kirk, Spock and McCoy find a scientific team dead, and their children who, unknown to the crew, have great powers at their disposal.

An alien force drives the crew of the Enterprise into brutal conflict with the Klingons.

While visiting a doomed planet, the landing party is subject to torturous experiments by powerful aliens.

The USS Enterprise ferries a spoiled princess whose betrothal to a royal Troyian is hoped will bring peace to a star system at war.

The Enterprise encounters two duo-chromatic and mutually belligerent aliens who put the ship in the middle of their old conflict.

Strange incorporeal aliens threaten the Memory Alpha station and the Enterprise.

The crew of the Enterprise encounter an immortal human in this science fiction variation on Shakespeare's The Tempest.

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