Episode Title: "MIRROR, MIRROR"
Production Number: 39
Original Air Date: 10-06-67
Captain Kirk is negotiating with the Halkan Council to get permission for the Federation to mine dilithium crystals on the Halkans' planet, but the peaceful Halkans refuse to let their crystals be used for any technology that could lead to violence in the future.
When Kirk and his landing party beam back to the U.S.S. Enterprise during violent magnetic ion storms, they find themselves in a parallel Universe, where the crew's behavior is more violent, and the I.S.S. Enterprise is a battleship serving the Empire, with orders from Starfleet Command to destroy the Halkans if they refuse to cooperate.
In this parallel Universe, Kirk became the captain of the I.S.S. Enterprise through the assassination of Captain Christopher Pike, and subsequently suppressed the Gorlan uprising through the destruction of the rebels' home planet, and executed 5,000 colonists on Vega Nine.
Kirk and his landing party work to delay the destruction of the Halkans' world, while trying to find a way back to their own universe. Kirk is assisted by his counterpart's woman, Marlena, and an advanced alien weapon called the Tantalus field, which can monitor his enemies aboard the ship, and make them instantaneously disappear.
Spock's counterpart uses a mind-meld on Dr. McCoy, and learns that he is from another Universe. Spock then assists the landing party in returning to their own Universe, in order to get his own captain and officers back. Spock theorizes that the Empire will be overthrown by Galactic revolt within 240 years, and Kirk urges him to take command of the I.S.S. Enterprise and set the Empire on a more logical course.
Factoid: Spock of the MIRROR UNIVERSE says, "One man cannot summon the future."
Dr. McCoy: "I'm a doctor, not an engineer."
Guest Characters: Lt. Kyle, *Lt. Marlena Moreau;
*Kirk, *Spock, *McCoy, *Sulu, *Scott, *Uhura, *Kyle, *Chekov, *Marlena Moreau
Alien Races: Vulcans, *Halkans
Starships: *I.S.S. Enterprise NCC-1701
KEY: [brackets]=illusions *star=first appearance