The Conscience of the King
If the William Shatner that exists only in the worst stereotypes was allowed to ghost-write an episode of Star Trek, what he would write would be The Conscience of the King (Memory Alpha; HD Video).
Badly written, poorly paced, and terribly acted, this episode is a mystery where you know who did it and how, and the only question is when Kirk will decide to do something about it. There’s a plot twist that’s so predictable it hardly deserves the name (I wrote that line twenty minutes in; the reveal is at forty-four minutes).
It does have two redeeming qualities, but they are minor. Uhura sings, which I find hilarious because of how out of place it seems. And Reilly returns, now transfered to Engineering but mercifully without a new, red shirt.
Grade
F