"What if you decide he is Kodos? What then? Do you play God, carry his head through the corridors in triumph? That won't bring back the dead, Jim."
"No, but they may rest easier."
Aside from SF Debris, I'm not sure other Star Trek fans are really talking up this episode -- which is a shame, because it's very, very good. Granted, the fact that the writing and the acting occasionally tip towards the melodramatic keeps The Conscience of the King from earning an A -- but the story and the message remain fundamentally sound.
Memory Alpha covers the episode here.
I think the first thing I really like about this episode is that it illustrates, once again, that Kirk is not simply Starfleet's biggest gigolo. Oh, I definitely roll my eyes at the brief romantic bits between Kirk and Lenore -- but then I remember that Kirk's motives in those moments can hardly be reduced to the call of his hormones. On the contrary, as Lenore herself observes later, Kirk is also using emotional manipulation to ply Kodos' daughter for information. And in case you're wondering, I think that's cool; I love it when the hero toes - or crosses - the line between honorable and dishonorable conduct because he's just so determined to get the bad guy. (See also: my undying love for DS9's In the Pale Moonlight.) Such moments reveal that our protagonist is human and therefore vulnerable to universal human temptations.
And speaking of those temptations: As the quote above implies, this is an episode in which Kirk grapples with his own baser inclination to seek revenge -- and that struggle reveals much that is admirable in Kirk's character. Given Kodos' indisputable guilt for the atrocities committed on Tarsus IV, Kirk has every reason to want, in McCoy's words, to "carry [Kodos'] head through the corridors in triumph." Instead, he keeps a tight reign on his instincts. He hesitates to act until all the evidence is in -- and in the climax, he prevents a resort to vigilante justice. All of this reveals that Kirk is an intelligent, ethically mature leader. While he never gives ground when it comes to a non-negotiable moral issue (more on that in a moment), he also doesn't go off half-cocked and do something that he will later regret.
The second thing I like about this episode is its refusal to countenance excuses for intrinsic evil. The key moment on this front comes when Kirk finally confronts Kodos in his quarters. In this scene, Kodos tries to rationalize his actions as governor of Tarsus IV, but Kirk firmly and repeatedly rebukes him:
"Kodos, whoever he was—"
"Or is. Kodos made a decision of life and death. Some had to die that others might live. You’re a man of decision, Captain. You ought to understand that."
"All I understand is that four thousand people were needlessly butchered."
"In order to save four thousand others. And if the supply ships hadn’t come earlier than expected, this Kodos of yours might have gone down in history as a great hero."
"But he didn’t. And history has made its judgment."
"If you’re so sure that I’m Kodos, why not kill me now? Let bloody vengeance take its final course! And see what difference it makes to this universe of yours."
"Those beautiful words, well acted, change nothing."
Whatever the difficulty of the circumstances, some decisions are so morally debased that they can never be acceptable -- and consulting the principles of eugenics to "cull the herd" falls into that category. Indeed, such a crime cries out for official retribution -- and happily, while Kirk stops Riley from shooting Kodos, he never backs down from this fundamental point.
As I noted above, the writing occasionally lacks subtlety. Still, this script is a strong character piece for Kirk.
I found Barbara Anderson's caterwauling at the end a bit much. On the other hand, Shatner, to his credit, is positively subdued.
Because this episode decries vengeance without losing sight of what justice and morality require, it earns a top mark on the theme.