An alien device on a primitive planet erases Captain Kirk's memory, and he begins a new life with the planet's indigenous people.

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.

The Enterprise travels with an alien ambassador whose appearance induces madness.

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.

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

Captain Kirk is caught between dimensions while the crew of the Enterprise works to retrieve him. All the while, the Tholians demand that the Enterprise leave their space.

Invisible "time-accelerated" aliens take over the Enterprise and attempt to abduct the crew for use as "genetic stock".

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

A race of overpopulated aliens abduct Captain Kirk to solve their problem.

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

Captain Kirk races against time to acquire plague-fighting minerals from a world in the midst of a civil uprising against a grievous social class disparity.

Kirk, Spock and McCoy are trapped in two parts of another planet's past - a world threatened with destruction when its sun goes supernova.