The Enterprise takes a Vulcan xeno-ecologist, T'Kalenayas, to Sarat for unknown reasons. Arriving, they find that the research station commander, Swifka, has called for them because a crop failure is causing famine among the natives. At length, he kidnaps T'Kalenayas, who has--along with everyone else--refused to interfere, citing the prime directive. In the end, Swifka is to be returned to star base, presumably under arrest, and T'Kalenayas stays behind to investigate whether the situation on Sarat can be slowly improved to prevent the famine without damaging the culture.
During these events, Spock expresses that he prefers the company of Vulcans, which causes some distress to Kirk, in particular.