This Side of Paradise (Episode)
The crew is astonished to find a colony thought to be dead is instead alive and flourishing The Enterprise arrives at planet Omicron Ceti III, where Kirk expects to find all the colonists dead because of the deadly Berthold rays to which they have been exposed for three years. But when a landing party beams down, colony leader Elias Sandoval informs them that everyone on the planet is quite well—including Leila Kalomi, a young botanist with whom Spock had worked six years before. Leila leads Spock to a clump of plants that spray him with their spores, liberating the Vulcan's emotions. Spock expresses his long-suppressed love for Leila. Other members of the landing party are exposed, plants are beamed up to the Enterprise, and before long everyone is affected. Then the captain discovers that strong emotional reactions are the antidote to the spores' effects, and tricks Spock into coming back aboard the Enterprise. He goads him into a fight, and barely avoids being killed by the Vulcan's superior strength. The conflict restores Spock to normal, and he assists Kirk in constructing an apparatus that frees the Enterprise crew and the colonists from the spores.