The Enterprise crew encounters a 200-year-old Earth probe, believed to be responsible for the destruction of an entire star system -- and brings it on board the ship.
A transporter accident sends Kirk, Scott, Uhura and McCoy to an alternate dimension, where the unscrupulous crew advance in rank through assassination, and the Enterprise is poised to destroy a world.
The Enterprise ferries a group of Federation diplomats to a peace conference, including Spock's father -- who falls deathly ill, forcing the Vulcan first officer to weigh the importance of his duty.
Kirk, Spock and McCoy arrive on an alien world to negotiate a mining treaty, but must protect the pregnant widow of the planet's murdered leader from a coup attempt. The Enterprise comes face-to-face with a Klingon war ship in orbit.
The crew of the Enterprise is stricken with an illness that causes rapid aging, incapacitating even the command staff -- and leaving the ship vulnerable to Romulan attack.
The Enterprise crew arrives on a space station to defend it from a possible Klingon attack -- but find that the biggest threat may come from a mass of gentle, furry creatures.
The crew find a civilization that has modeled itself after mobsters of 1920's Earth, and Kirk and Spock must play their roles in order to end a lifestyle of constant violence.
The Enterprise encounters a giant space amoeba believed to be responsible for the destruction of a Federation starship -- and an entire solar system. Kirk must choose between Spock and McCoy for a suicide mission.
Kirk returns to a primitive, peaceful world he visited once before, only to discover that the Klingons have armed a tribe in conflict with his friend's.
The Enterprise picks up a group of disembodied aliens, who are allowed to assume the bodies of three of the crew in order to construct new forms of their own -- though they may not be willing to give them up.
The Enterprise investigates the disappearance of a Federation historian, and the crew discovers that the world he is on has shaped itself in the oppressive image of Nazi Germany.
The Enterprise is hijacked by a group of explorers from another galaxy, who intend to use the ship to make the long journey back home -- and turn most of the crew into small mineral blocks.
The Enterprise is chosen to be the test ship for a new, highly-advanced computer -- which proceeds to take control of the vessel and lead it into a deadly war games scenario.
Kirk, Spock and McCoy are captured by a Romanesque civilization while investigating the destruction of a Federation ship, and are forced to fight in a gladiator arena for the local population's entertainment.
The Enterprise travels back to 20th century Earth, and finds a man from an alien world attempting to manipulate human history -- who claims to be preventing Earth from destroying itself.
