The Conscience of the King
A troupe of Shakespearean actors arrives on the Enterprise, yet Kirk believes their leader to be a political criminal and murderer.
The most common complaint about this episode is that it's "not science fiction," but a thoughtful drama is really preferable to another monster tale or poorly rendered battle. Kodos the Executioner is rare: a complex villain who's not simply insane. (Though his daughter is.) He is a man reformed but retaining a disturbed edge. Kirk learns revenge isn't the answer, and that personal vendettas shouldn't overtake his duties. The discussions between Spock and Bones are particularly dynamic, as is their conversation with their fixated captain. A similar situation arises in Obsession. Nice to see Riley return, though in a more serious capacity. The Trek writers have always been fond of Shakespeare, and the allusions and parallels are effective here. Elaborate effects are not needed when a script has true themes and drama.
Spock Saves the Day: The Vulcan attempts to curb his captain's irrational behavior, and partly succeeds with an unlikely ally: McCoy.
Oops: Uhura, Spock called and wants his lyre back . . .
Developments: Once the Vulcan's made up his mind, he doesn't waver. While Bones frets as to whether or not it's really Kodos, and whether Jim is in danger, Spock knows. Also, his bickering with the doctor is set aside whenever there's a threat to their mutual friend Kirk. They aren't afraid to confront him, and can officially overpower him.