The Enemy Within
Episode 6 of 30 within Season One. Item 6 of 90 overall.
Production number 6149-05.
Richard Matheson - Writer
Leo Penn - Director
398 votes

Stardate:1672.1--1673.1 A transporter malfunction separates Kirk into two people: a kind and gentle vacillitating version, and a strong-willed arrogant Kirk who gives in to his every bestial urge.

Elsewhere, when the divided Kirks start to die, Spock and Scotty must work to reverse the split and save him, as well as repair the transporter so they can beam up a stranded crew.

original airdate--October 06,1966   

network: NBC

music: "Theme from Star Trek" "Where No Man Has Gone Before" by Alexander Courage 


Alien Races: Alpha 177 quadrupeds 

Log Entries:

  • Captain's log, stardate 1672.1. Specimen gathering mission on planet Alpha 177. Unknown to any of us during this time a duplicate of me, some strange alter ego, had been created by the transporter malfunction.
  • Captain's log, stardate 1672.9. On the planet's surface, temperatures are beginning to drop; our landing party there in growing jeopardy. Due to the malfunction of the ship's transporter, an unexplained duplicate of myself definitely exists.
  • Captain's log, stardate 1673.1. Something has happened to me. Somehow in being duplicated, I have lost my strength of will. Decisions are becoming more and more difficult.
  • Captain's log, stardate 1673.5. Transporter still inoperable... my negative self is under restraint in sickbay... my own indecisiveness growing... my force of will steadily weakening. On the planet condition critical, surface temperature is 75 degrees below zero. Still dropping.
  • Captain's log, stardate 1674.1, entered in by Second Officer Spock. Captain Kirk retains command of this vessel, but his force of will rapidly fading. Condition of landing party critical. Transporter unit still under repair.


Space: the final frontier. These are the voyages of the starship Enterprise. Its five-year mission: to explore strange new worlds, to seek out new life and new civilizations, to boldly go where no man has gone before.

Klingon: logh: HeH Qav'e'. DaH 'entepray' Duj lengmey lutalu'. Qu' vagh-DIS: Huj chu' qo', yISam yIn tayqeq chu', vay' boldly nuqDaq V pagh 'ej explore.

related items

Previous episode :
005 The Naked Time
Next episode :
007 Mudd's Women

alternative title

Also known as - Klingon=rInpa' jagh

regional titles

The Enemy Within
The Enemy Within
Kirk : 2 = ?
The Enemy Within
Il duplicato
El propio enemigo