Stardate 3417.3: The Enterprise arrives at Omicron Ceti III, hoping to find surviving colonists who have been exposed to deadly berthold rays for three years. Surprisingly, the colonists are not only alive but in perfect health. While McCoy tries to unravel the mystery, Kirk attempts to convince the colonist's leader, Elias Sandoval, that an evacuation of the planet is imperative. None of the colonists, however, want to leave despite their lack of accomplishments and the deadly effects of the berthold rays. One of the colonists, Leila Kalomi, had met Spock six years earlier and fell in love with him. Eager to keep him on Omicron Ceti, she exposes Spock to a plant that contains spores which cause feelings of peace and contentment. When the spores manage to break down Spock's emotional barriers, he suddenly finds happiness and falls in love with Leila. Soon, the spores infect all of the landing party, except Kirk, and are beamed up to the Enterprise where they quickly take hold of the entire crew and compel them to join the colonists on the planet. While alone on the Enterprise, Kirk is finally overpowered by the spores and prepares to leave the ship. But, just as he is about to beam down, the thought of leaving the ship causes a violent reaction which destroys the spores in his body. Armed with a theory and a large club, Kirk tricks Spock into beaming back aboard where he taunts the Vulcan into a fight which destroys the spores. They then use subsonic sound waves to provoke a mass brawl on the planet below. Sandoval, no longer influenced by the spores, realizes that the colonists have accomplished nothing in their three years on Omicron Ceti and agrees to leave with the Enterprise and relocate to a planet where the colony is free to make progress and grow.