25 user 6 critic

The Enemy Within 

A transporter malfunction splits Captain Kirk into two halves: one meek and indecisive, the other violent and ill tempered. The remaining crew members stranded on the planet cannot be beamed up to the ship until a problem is fixed.


Leo Penn


Richard Matheson, Gene Roddenberry (created by)




Episode complete credited cast:
William Shatner ... Capt. Kirk
Leonard Nimoy ... Mr. Spock
DeForest Kelley ... Dr. McCoy
Grace Lee Whitney ... Yeoman Janice Rand
George Takei ... Sulu
James Doohan ... Scott
Ed Madden Ed Madden ... Fisher (as Edward Madden)
Garland Thompson Garland Thompson ... Wilson
Jim Goodwin Jim Goodwin ... Farrell


While beaming back aboard the Enterprise, a transporter malfunction results in two vastly different Captain Kirks being beamed aboard. His personality has in effect been split into two. One Captain Kirk is weak and indecisive, fearful of making any kind of decision; the other is a mean-spirited and violent man who likes to swill brandy and force himself on female crew members. Meanwhile, as Scotty struggles to repair the transporter, the landing party is stuck on the planet below with temperatures falling rapidly. Written by garykmcd

Plot Summary | Plot Synopsis


TV-PG | See all certifications »






Release Date:

6 October 1966 (USA) See more »

Company Credits

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Technical Specs


Sound Mix:




Aspect Ratio:

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Did You Know?


Yeoman Janice Rand's quarters are located here: 3C 46. However, in Star Trek: The Original Series: Charlie X (1966), Rand's quarters are 3F 125. See more »


There appears to be no in-universe explanation of why no transporter engineer was required to work the controls to beam up "evil Kirk". The transporter room was empty, so the transporter initiated and completed the beam up all on its own. See more »


Sulu: Can you give us a status report, Captain? Temperature's still dropping. Now 41 degrees below zero.
Captain James T. Kirk: We've located the trouble. It shouldn't be much longer.
Sulu: Do you think you might be able to find a long rope somewhere and lower us down a pot of hot coffee?
Captain James T. Kirk: I'll see what we can do.
Sulu: Rice wine will do if you're short on coffee.
See more »

Alternate Versions

Special Enhanced version Digitally Remastered with new exterior shots and remade opening theme song See more »


Referenced in Weird Science: A Tale of Two Lisas (1994) See more »


Theme From Star Trek
Written by Alexander Courage
See more »

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User Reviews

Dr. Jekyll and Captain Kirk
24 April 2014 | by HitchcocSee all my reviews

Kirk is divided in half. He, like the Stevenson Jekyll/Hyde character becomes two people. One exhibiting an animalistic being and the other an outer space Casper Milquetoast. The problem is that the two look exactly. It allows William Shatner to bring out his ultimate ham. He mugs and sneers as the evil side while he whimpers indecisively as the other half. The key is to not destroy everything while the lecherous Kirk is chasing Yeoman Rand, trying to assault her sexually. This becomes an uncomfortable series of events. In some ways, it is quite laughable; on the other hand, it is deadly serious. Spock and the others are in a quandary because they must figure out what is going on. Kirk comes and goes and they are suspicious, but they have no reason to suspect anything other than the fact that he is an incredible mess. Science to the rescue.

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