After losing his entire crew to an alien planet-eating machine, Commodore Matthew Decker pulls rank on Kirk in order to play a game of cat-and-mouse with the mechanical adversary. His efforts to destroy the menace place the Enterprise in grave danger.

Two powerful aliens threaten the well-being of the Enterprise and her crew with their magical powers.

The crew of the Enterprise visits a mysterious and deadly paradise planet which they discover is controlled by a machine called Vaal

A transporter mishap slips Captain Kirk and his companions into a parallel Universe, where the Enterprise serves a barbaric Empire instead of the Federation. This episode spun off several plotlines in Deep Space Nine and Enterprise.

The crew of the Enterprise deals with Nomad—an indestructible, planet-destroying space probe that thinks Kirk is its creator. Star Trek: The Motion Picture was in part an expansion of this episode.

When Mr. Spock begins behaving aggressively, Kirk discovers his first officer must return home to Vulcan to be married, or die. Kirk disobeys his orders to save Spock, only to find the unbalanced Vulcan at his throat when the bride forces Spock

The crew of the Enterprise are held captive by an alien who claims to be the Greek god Apollo.

Aliens force Kirk and Spock to battle illusionary villains in a test of good versus evil.

Kirk, Spock and McCoy are trapped in the past on a world threatened by a Nova.

Kirk’s consciousness becomes trapped in the body of a woman bent on killing him and taking over his command while inhabiting his body.

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

The crew of the Enterprise encounters an immortal human who lives as a recluse on his own planet.