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E1 Amok Time
First Officer Spock returns to his home world for a brutal Vulcan mating ritual.
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E2 Who Mourns for Adonais?
The crew of the Enterprise are held captive by an alien who turns out to be the Greek god Apollo.
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E3 The Changeling
The crew of the USS Enterprise deals with an indestructible planet-destroying space probe.
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E4 Mirror, Mirror
A transporter mishap swaps Captain Kirk and his companions with their evil counterparts in a parallel universe. In the so-called Mirror Universe, the Enterprise is a ship of the Terran Empire, an organization as evil as the United Federation of Planets is benevolent.
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E5 The Apple
The crew of the Enterprise visits a mysterious paradisical planet controlled by a computer that is served by the local inhabitants.
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E6 The Doomsday Machine
The starship Enterprise and its heavily-damaged sister ship, the USS Constellation, must work together to stop an alien planet-killing machine headed for the heart of Federation territory.
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E7 Catspaw
Two powerful aliens threaten the well-being of the Enterprise and her crew.
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E8 I, Mudd
Captain Kirk has a second run-in with the conman, Harry Mudd. Mudd is now the supreme ruler of a planet of androids who cater to his every whim.
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E9 Metamorphosis
A shuttle crew from the USS Enterprise encounters a man out of history and his mysterious alien companion.
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E10 Journey to Babel
The Enterprise must transport dignitaries to a peace conference, with an assassin on the loose.
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E11 Friday's Child
The crew of the Enterprise become entangled in a planet's tribal power struggle.
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E12 The Deadly Years
Strange radiation exposes the command crew of the Enterprise to the effects of rapid aging.
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E13 Obsession
Captain James T. Kirk becomes obsessed with destroying a deadly entity he once encountered in his youth.
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E14 Wolf in the Fold
A series of bizarre murders points to Mr. Scott as the prime suspect.
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E15 The Trouble With Tribbles
The Enterprise must protect a very important shipment of grain from both Klingons and some adorable creatures called tribbles.
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E16 The Gamesters of Triskelion
Captain Kirk and his companions are abducted into slavery and trained to fight as gladiators for the gambling entertainment of three disembodied beings.
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E17 A Piece of the Action
The Enterprise visits a planet with an Earth-like 1920s gangster culture.
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E18 The Immunity Syndrome
The crew of the Enterprise encounters an energy-draining field which may be able to destroy the galaxy.
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E19 A Private Little War
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.
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E20 Return to Tomorrow
Ancient alien minds are given control of Captain Kirk's and First Officer Spock's bodies.
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E21 Patterns of Force
The crew of the Enterprise tracks down a Federation observer on a planet dominated by a "Naziesque" regime.
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E22 By Any Other Name
Beings from another galaxy commandeer the Enterprise in an attempt to return home.
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E23 The Omega Glory
Captain Kirk must find the cure to a deadly disease and put an end to another Starfleet captain's cultural interference.
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E24 The Ultimate Computer
A skeleton Enterprise crew are assigned to test a revolutionary computer system that is given total control of the ship.
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E25 Bread and Circuses
The Enterprise crew investigates the disappearance of a ship's crew on a planet that is a modern version of the Roman Empire.
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E26 Assignment: Earth
While back in time observing Earth in 1968, the Enterprise crew encounters the mysterious Gary Seven who has his own agenda on the planet.