Richard Matheson’s The Enemy Within was a good story. Gene Roddenberry made it great.

The episode we see on screen is a thoughtful examination of human duality, of the balance between the positive and negative impulses and qualities that make up humans. We learn that we cannot function without this balance.  

That central meaning was missing in Richard Matheson’s story outlines and in his first draft script. In those versions of the story, the “double,” as the second iteration of Kirk is called, is evil but there is no explanation of why, while the “good” Kirk is essentially unchanged except that both are physically weak, as if their strength has been halved. There is even the suggestion that the two have lost mass in the split, an idea that Roddenberry and others dismissed as the Kirks would then have to appear physically smaller on screen. 

Matheson submitted his first story outline in early April 1966, with a revised version delivered about two weeks later. His first script was dated April 25. On April 26, Roddenberry sent a memo to Matheson with a number of suggested improvements. The most interesting one, and the idea that absolutely elevates the story, is that both Kirks have suffered a loss. He wrote:

…we should begin to suggest that the real Kirk has been changed by all this too. Deprived of the negative side of his career, he must begin to lose some of the strength that positive-negative gives a man. Decisiveness would be one of the first things he’d have trouble with. 

Important, however, his intelligence would tell him something is wrong and he would struggle against all of this. He would know intellectually that his commanding of the ship demands balancing the safety of many against the safety of few, etc. 

We see this idea play out exactly as Roddenberry suggested halfway through the screened episode, with the “good” Kirk talking to McCoy and Spock while the other is strapped to a bed in sickbay:

Spock: We have here an unusual opportunity to appraise the human mind, or to examine, in Earth terms, the roles of good and evil in a man. His negative side, which you call hostility, lust, violence, and his positive side, which Earth people express as compassion, love, tenderness.

McCoy: It’s the Captain’s guts you’re analysing. Are you aware of that, Spock?

Spock: Yes, and what is it that makes one man an exceptional leader? We see indications that it’s his negative side which makes him strong, that his evil side, if you will, properly controlled and disciplined, is vital to his strength. Your negative side removed from you, the power of command begins to elude you.

Kirk: What is your point, Mister Spock?

Spock: If your power of command continues to weaken, you’ll soon be unable to function as Captain. You must be prepared for that.

McCoy: You have your intellect, Jim. You can fight with that!

Roddenberry’s examination of what it means to be human is far more interesting than Matheson’s take, which towards the end of his story was closer to a monster hunt. 

Input from NBC 

Stan Robertson was an NBC executive and the Program Manager for Star Trek. While typically an annoyance to the producers, he often had good ideas. That was not the case with this episode, however.

His June 10, 1966 memo, written four days before the cameras rolled on Enemy, offered feedback that would have ruined the episode. He wrote to Roddenberry:

We would further suggest at this time:

1. That there be frequent intervals during the telling of our story in which we make it clearly understood that the “Alter Ego” is not the “real” Kirk, but only a manifestation of some technical failure in the Transporter device which caused “unexplained” changes to occur in anything passing through.

2. That we minimize or eliminate completely the weakness in the “real” Kirk, such as the failure of his ability to make command decisions in the face of the appearance of his “Alter Ego”. We would think that, confronted with this great challenge, he would rise to greater heroic heights, be more definite, the complete antithesis of the “Alter Ego”. 

3.  That there be a definite resolution in the story of the “Alter Ego”, clearly indicating that he is dead and gone for all times. Further, that what has occurred could have happened to anyone and does not necessarily indicate that the negative qualities, as materialized in the “Alter Ego”, are the secret inner cravings of our hero.

This is the opposite of everything Roddenberry was trying to do with the episode and would have drained all meaning from it. 

But the worst bit made it through 

The Enemy Within is a great episode of Star Trek — except for the bit at the end. In the final scene on the bridge, a smirking Mr. Spock makes a grievously inappropriate comment to Yeoman Rand. Shortly after she is almost raped by her captain, the first officer suggests to her that “The imposter had some interesting qualities, wouldn’t you say, Yeoman?” 

That same message was included in Matheson’s story outline, except this time he put the offensive words in Rand’s mouth. Kirk has just said that he needs his “darker side” and that “The challenge is to master that side, wishing neither to destroy it nor to flee from it.” He then asks Rand “Isn’t that right?” to which she replies:

“Yes,” she answers. “It would be a shame to destroy it.” Is that a twinkle in her eye? “It has some very interesting qualities.” 

Both versions of this scene are just gross. Roddenberry’ understanding of character and the conviction he showed in ignoring NBC’s notes elevated this episode. If only he could have also ditched this misogyny.