 The Enterprise suffers a potential lethal epidemic of Rigelian fever. Luckily the crucial mineral ingredient for the cure, ryetalyn, can be collected from a supposedly uninhabited planet, but the landing party finds it controlled, with incredible technical superiority, by an earth-man called Flint who wants the ship gone within hours but instructs his robot M4 to help McCoy gather and process the ryetalyn. Kirk and Spock are meanwhile entertained in his fabulous palace, where the captain is increasingly enchanted by his naive, beautiful young female ward Rayna, while Spock finds his treasures include authentic, yet recently produced works of art by long dead artists Leonardo da Vinci and Johannes Brahms...