Episode Title: "THE ALTERNATIVE FACTOR"
Production Number: 20
Original Air Date: 03-30-67
Stardates: 3087.6, 3088.3, 3088.7
The U.S.S. Enterprise is investigating a lifeless, uncharted planet when violent force waves disrupt the entire quadrant of space. At the same time, a human is detected on the planet. Captain Kirk leads a landing party to the planet, and finds a crazed man named Lazarus, who claims to be chasing a monster who destroyed his planet.
Starfleet Command determines that the effect originating at the planet is causing complete disruption of normal magnetic and gravimetric fields, time warp distortions, and possible radiation variations in every quadrant of the Galaxy. Starfleet Command orders the Enterprise to investigate the phenomenon while all other Starfleet personnel within 100 parsecs are evacuated.
Two dilithium crystals are stolen, and Lazarus claims that his enemy took them. Lazarus asks for more crystals so he can destroy the threat. Commander Spock detects an unexplained radiation source on the planet, but nothing else is detected. Lazarus says that his vehicle on the planet is a time ship, and he is a time traveller chasing his enemy through time, and this dead planet was once his home before it was destroyed.
Kirk and Spock theorize that the enemy Lazarus is chasing is his double from a parallel, antimatter universe, which causes the space disruptions when a link opens between the two universes. Lazarus steals two dilithium crystals and returns to his ship on the planet, but Kirk follows him and the ship transports Kirk into the antimatter universe, where he meets the more rational, antimatter double of Lazarus.
The double tells Kirk that his people discovered a corridor to travel between two universes, but Lazarus became insane knowing he had a double in another universe, and is obsessed with destroying the double. If they ever meet one another in either universe, the meeting of matter and antimatter would destroy the universe, so Kirk returns to his own universe and forces Lazarus into the corridor between universes, where his antimatter double is waiting, and the two of them remain there battling for eternity, keeping both universes safe.
Factoid: Captain Kirk has 430 men to worry about.
Dr. McCoy: "As we both know, I'm a bright, young medic with a miraculous touch."
Dr. McCoy: "I'm just a country doctor."
Guest Characters: Lt. Leslie, *Lt. Masters
KEY: [brackets]=illusions *star=first appearance