#12: This Side of Paradise
In case you forgot: Spores from some plants are keeping colonists alive and immune to the deadly rays bombarding their planet, at the cost of their ~ambition~ or something. Everyone on The Enterprise gets infected and starts zoning out, but Kirk is made of sterner stuff and talks himself and Spock out of it. They save the day and take the newly spore-less colonists back home.
"This Side of Paradise," like so many other great episodes, opens up quickly with a mystery and keeps piling on more clues and insights at a good pace. The colonists who should be dead are all freakishly healthy; there aren't any other animals on the planet; they haven't planted or harvested any more than just what they've needed to eat. What is going on down here? There is some legitimately frightening stuff going on during all of this, too. When Elias and Colomi are talking about Spock and whether he should stay, it's pretty freaking sinister.
Watching Kirk berate Spock is a really great moment, and by great I mean awful, because you know Kirk doesn't want to do it. Not only because Spock would outclass him in a proper fight, but because to save his best friend he has to use every weakness, every sensitive spot he knows about Spock to save him.
Not sure how I feel about giving Spock a love interest, it seems...uncomfortable. It's touching to see him feel bad about abandoning her, I guess, but it seems very out of character. It was great how his initial reaction to the spores was HOLY GOD IT HURTS; I think I would have liked the episode even better if the spores, instead of making him happy and healthy, had made him seriously ill.
The moral of this story is also a mixed bag for me. The colonists seem to have genuinely happy lives, weird plant spores aside. It's not like they've been assimilated into some giant anonymous hivemind. They've all retained their individual personalities, memories, and experiences; they're just incredibly happy. Is that really so awful? Having ambition and purpose and goals is essential to mental well-being in American society, sure, but it seems too specialized a sentiment ("Work hard! Be productive! Accomplish things!") to be a truly universal fact.