- This article is about the Star Trek episode. For other, similarly titled science fiction, see: The Enemy Within (disambiguation).
"The Enemy Within" is an episode of Star Trek: The Original Series first broadcast October 6, 1966. It is a first season episode, #5, and was written by Richard Matheson and directed by Leo Penn.
Quick Overview: A transporter mishap creates Captain Kirk's evil twin.
 Kirk's evil twin, "The Enemy Within" On stardate 1672.1, the USS Enterprise, under the command of Captain James T. Kirk, is on a geological mission of the planet Alfa 117. Down on the planet, Geological Technician Fisher falls from an embankment and injures his hand. He is immediately beamed back to the Enterprise for medical treatment, however during the beam up, the transporter system acts funny. Nearly losing the technician, Mr. Scott immediately checks over the transporter equipment but finds nothing wrong. He only notices magnetic dust from some ore samples covering Fisher's uniform when the technician materializes in. Scotty tells him to have the uniform decontaminated.
Soon Captain Kirk beams back to the ship and this time the transporter seems to work smoothly. Kirk and his officers then leave the area, however a moment later a second Captain Kirk materializes on the transporter pad. Since no one was left in the transporter room, the crew is unaware of this second Kirk's arrival. This Kirk is actually a materialization of the true Captain's split persona, a physical manifestation of his more selfish and evil qualities.
The first thing the "evil" Kirk does is head to sickbay where he demands a drink of brandy from Dr. McCoy. McCoy can't figure out this sudden aggressive moodswing displayed by his captain.
Back in the transporter room, Scotty receives an animal specimen the landing party beams up from the planet. It is a small horned dog-like creature, however two dogs arrive on the transporter pads, one extremely vicious and the other very timid, yet both look identical. Confirming the team only beamed one animal to the ship, Scotty realizes something is very wrong with the transporter and he is forced to strand the remaining landing team (including Lt. Sulu) on the planet until further notice.
The shuttlecraft were also unavailable to retrieve the landing party. The reason for this is that the studio decided to defer constructing the shuttlecraft sets until the second season of the series.
Meanwhile, evil-Kirk, appearing drunk and disorderly, enters the quarters of Yeoman Janice Rand, and lies in wait for her. When she arrives he grabs hers and tries to force himself upon her. She manages to fight back, and scratches his hand with her sharp nails and then runs to crewman Fisher for help. Unfortunately, the evil Kirk incapacitates Fisher before he can call for Mr. Spock's assistance.
Simultaneously elsewhere on the ship, the good Captain Kirk begins to show signs of weakness, losing both his ability to make decisions and give orders to the crew. He throws himself about the bridge in an apparent nervous breakdown, and Spock can do little to help him at the moment.
The evil-Kirk manages to acquire a phaser from a crewman who he knocks unconscious, then goes hiding down on the lower decks of the ship. Anticipating his moves, Spock locates the evil-Kirk and disables him with a Vulcan nerve pinch. Now that the sinister half of Kirk is disabled, Spock doesn't know for sure how to proceed next, since the evil-Kirk is showing fatigue and signs that he may be dying.
It is quickly surmised that neither Kirk can survive in this separated state for long, and time is running out, not only for the Captain, but for the crew stranded on the planet who report a rapid drop in surface temperature and fear they could freeze to death.
Scotty reports that an ionizer component of the transporter is damaged, and that it will take a week to repair, however Spock pressures Mr. Scott indicating that the Captain and the landing party doesn't have that much time. Mr. Spock and Scotty get to work, and jury-rig a connection to power the transporter off the ship's impulse engines. They manage unsuccessfully to recombine the dog-creature, and it soon dies as a result of the strain. Not giving up hope, Scotty continues to work on the problem.
In the meantime, good Kirk leads his dark half to the transporter room, however the evil-Kirk manages to overpower him and rushes off to the bridge where he orders the ship to leave orbit. Good Kirk follows him there and confronts him. Eventually evil-Kirk is restrained and both Kirks are taken back to the transporter where Scotty claims everything should work now. With fingers crossed Scotty beams both Kirks away, and finally a single Kirk returns. Checking him over McCoy believes the Captain is "all there" once again. Scotty then brings back the landing party, who aside from a little frost bite, are fine.
External Links
"The Enemy Within (http://www.memory-alpha.org/en/index.php/The_Enemy_Within)" article at Memory Alpha, a Star Trek wiki
| 
