Star Trek: Season 1, Episode 5

The Enemy Within (6 Oct. 1966)

TV Episode  |   |  Action, Adventure, Mystery
Your rating:
    1 2 3 4 5 6 7 8 9 10 -/10 X  
Ratings: 7.8/10 from 1,376 users  
Reviews: 14 user | 10 critic

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.



, (created by)
Watch Episode
0Check in

Watch Now

Free at IMDb


User Lists

Related lists from IMDb users

a list of 291 titles
created 17 Jun 2012
a list of 21 titles
created 23 Jan 2013
a list of 44 titles
created 03 Jun 2013
a list of 25 titles
created 16 May 2014
a list of 30 titles
created 27 May 2014

Related Items

Search for "The Enemy Within" on

Connect with IMDb

Share this Rating

Title: The Enemy Within (06 Oct 1966)

The Enemy Within (06 Oct 1966) on IMDb 7.8/10

Want to share IMDb's rating on your own site? Use the HTML below.

Take The Quiz!

Test your knowledge of Star Trek.
« Previous Episode | 6 of 80 Episodes | Next Episode »





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


See all certifications »




Release Date:

6 October 1966 (USA)  »

Company Credits

Show detailed on  »

Technical Specs


Sound Mix:


Aspect Ratio:

1.33 : 1
See  »

Did You Know?


The original script called for Spock to karate chop Kirk to subdue him. Leonard Nimoy felt that this would be an uncharacteristically violent act for a peace-loving species like the Vulcans so he came up with a pincer-like grasp on the neck that has since become known as the Vulcan Nerve Pinch and become one of the character's most famous gimmicks. See more »


(at around 25 mins) The split-screen becomes obvious when the evil Kirk is lying on the floor: two sets of knees can be seen where the seam is. 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?
See more »


Referenced in Buffy the Vampire Slayer: The Replacement (2000) See more »


Theme From Star Trek
Written by Alexander Courage
See more »

Frequently Asked Questions

This FAQ is empty. Add the first question.

User Reviews

Kirk vs. Kirk
30 March 2009 | by (Italy) – See all my reviews

The Enemy Within is one of the finest episodes of Star Trek's first season, and its central idea has gone on to inspire similar scenarios in other genre shows, most notably Buffy The Vampire Slayer (see episode The Replacement in Season 4). It deals with a classic theme of horror and sci-fi literature, the double, and gives William Shatner the chance to have lots of fun with his role(s).

Sticking with formula, the episode starts with a patrol exploring a new planet. Unfortunately, when it's time to beam them back up on the Enterprise, the transport system starts malfunctioning, which results in Captain Kirk being literally split in two: one half is calm and rational, the other determined and impulsive. This triggers a race against the clock, since neither Kirk can survive without the other part, but also because if the transport device isn't fixed in time, Mr. Sulu and the other crew men left on the planet will freeze to death.

Having a double of a well known character is always interesting, whether it's an impostor, a robot or something different altogether. In this case, what really makes the story interesting is the fact that the "replacement" Kirk isn't a villain in the proper sense of the word: he's just a specific part of the captain's personality, with no rational components to keep the more violent sides of his nature under control. As such, The Enemy Within is a peculiar spin on the traditional Jekyll/Hyde "myth", made possible by the infinite possibilities of science-fiction storytelling.

More important, though, is what the episode allows in terms of performance: just like Naked Time gave some cast members the opportunity to fool around, this time Shatner has the unique privilege of being able to take Kirk (well, part of him, actually) to some darker places, expanding on the previous episode's idea of the character being torn between duty and private desires. It adds lots of tension, but it's also a very funny double portrayal, and one of the key ingredients of Trek's long-lasting success.

5 of 8 people found this review helpful.  Was this review helpful to you?

Message Boards

Recent Posts
Anton Karidian - hero or villan? josephturner1975
How much? McCartney42
The Women of the Original Star Trek.: Majel Barrett gavbrown01
The Women of the Original Star Trek: France Nuyen gavbrown01
The Women of the Original Star Trek gavbrown01
Dagger of the Mind AardvarkRatnik
Discuss The Enemy Within (1966) on the IMDb message boards »

Contribute to This Page

Create a character page for: