An alien invader steals Spock's brain to operate her civilization's central control system, and the crew must locate it and find a way to return it to his body before Spock dies.
Captain Kirk takes the ship on a dangerous, secret mission into Romulan space, in an attempt to acquire a cloaking device. Spock's loyalties are tested by a beautiful Romulan commander.
Kirk is stranded on a primitive world when an alien device strikes him with amnesia. As the captain falls in love and becomes a part of the natives' world, the Enterprise searches for a way to save the planet from an asteroid collision.
The Enterprise finds a group of children who have survived a mass-suicide, with help from a powerful alien entity -- who leads them in taking over the ship to find a new planet for him to control.
The Enterprise hosts a Medusan ambassador, whose physical appearance causes madness in humans. But when a distraught scientist maroons the ship beyond our galaxy, Spock must mind-meld with the alien to find the way home.
After trespassing into Melkotian space, Kirk and four of the crew find themselves in an alien-created reinactment of the deadly battle at the OK Corral.
Captain Kirk is forced to bring a group of angry Klingons on board, which quickly escalates into a battle for control of the ship -- with both groups being manipulated by a malevolent alien entity.
The Enterprise investigates a starship that is phasing out of existence, and Captain Kirk is lost. A pair of Tholian ships attack as a mysterious illness threatens to drive the crew insane.
A group of super-powerful aliens take control of the crew for their own amusement. Kirk and the others must discover the source of their amazing powers if they are to counter them.
An alien species attempts to use the Enterprise crew to save their dying race, drawing Captain Kirk into their own rapidly-accelerated state of existence.
Kirk, Spock and McCoy are captured and brought to an alien laboratory, where they are tortured one-by-one in order to test a beautiful, empathic healer's capacity for self-sacrifice.
When the Enterprise ferries a reluctant bride to her wedding with the leader of a warring planet, Kirk attempts to educate her in the ways of her new culture. But a Klingon attack threatens the peace her marriage would bring.
Kirk and Spock deliver a new medicine to a subterranean prison for the criminally insane, only to find out that one of the prisoners -- once a starship captain -- has taken over.
Two alien men come on board the Enterprise, bringing their war of racial bigotry with them. Kirk tries to mediate the conflict, but his patience runs out when one of them attempts to seize control of the ship.
While on a diplomatic mission to a world free of disease -- but plagued by over-population -- Kirk finds himself alone with a woman on a precise replica of the Enterprise.
The Federation's central library facility is wiped out by non-corporeal entities, who seek out the Enterprise and take the body of a young lieutenant as a host.
The crew is infected with a deadly plague, and seek the antidote from a world inhabited solely by an enchanting woman and a man straight out of Earth's history.
Seeking the cure to a planet-wide plague, Captain Kirk and his crew find themselves in the middle of a conflict between the miners of Ardana and the ruling class, who live in a city in the clouds.
An alien creature locks the Enterprise crew in combat with history's most notorious villains in a test of good versus evil, conjuring great heroes from the past to fight along side them.
The Enterprise discovers a massive library on a deserted world where the sun is about to go nova, and Kirk, Spock and McCoy are accidentally sent into dangerous periods in the planet's history.
Kirk's jealous former lover secretly exchanges bodies with the captain, allowing her to finally command a starship -- and trapping him in her radiation-stricken body.
