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 the problem is fixed.



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Episode complete credited cast:
Ed Madden ...
Fisher (as Edward Madden)
Garland Thompson ...
Jim Goodwin ...


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


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Release Date:

6 October 1966 (USA)  »

Company Credits

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Technical Specs


Sound Mix:


Aspect Ratio:

1.33 : 1
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Did You Know?


Kirk's alternate green wrap-around uniform was introduced so that the audience would be able to tell the difference between the good Kirk and the evil Kirk. See more »


When Sulu, stuck on Alpha 177, comments on his communicator about "the skiing season opening down here" to Good Kirk in the briefing room, Spock enters, sits at the computer console and interrupts their discussion, pressing his communicator button on his console. The communication console's white "in use" light does not illuminate yet Spock clearly makes contact with Sulu. See more »


Sulu: We're using hand phasers to heat the rocks. One phaser quit on us, three still operating. Any possibility of getting us back aboard before the skiing season opens down here?
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Referenced in Saturday Night Live: William Shatner/Lone Justice (1986) See more »


Theme From Star Trek
Written by Alexander Courage
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User Reviews

it's cheesy, yes, but a lot of fun as the whole Jungian thing pans out
21 October 2007 | by (United States) – See all my reviews

Let it be known- The Enemy Within is not great art. But it does come close to being a great Star Trek episode. Mostly because, in a way, splits down the path of William Shatner as an actor, or how much of an actor he can ever be. After a faulty teleportation back up to ship, ol Kirk is now two, with a doppelganger that beats people to a pulp and makes crude sexual advances to a worker on the ship (probably one of the first instances of attempted rape shown on prime-time TV at the time), while the other 'real' Kirk has lost his will to lead- he's unable to make decisions because his 'evil' side is really the one that takes charge to lead. But what to do as Soolu is stuck on an icy planet? This is all the stuff of pot-boilers, where you keep watching just to see what will make the Kirk's tick- or not- next. It's utterly classic comedy (maybe unintentionally so, maybe meaning to be) as 'evil' Kirk tries to take over the ship incognito, but gets caught when he tries to get the ship away from Soolu and the others!

But then there's the existential crisis of 'good' Kirk, as he doesn't have any real resolve as a leader, except in regards to putting himself, literally it seems, back together. In a way it's kind of trashy, and I could see why one or two Trekkies might find it sub-par. But it does give Shatner lots of freedom as an actor, unlike most of the time where he inspires the best in imitators, and I liked the dichotomy of the psychology present, even as dated as it is. How does one balance the good with the bad? Control, it seems, at least is you're James Tiberius Kirk- which includes libido.

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