The Enterprise transports the Medusan Ambassador Kollos; his telepathic interpreter, Dr Miranda Jones; and Engineer Laurence Marvick. Only Vulcans and those trained in Vulcan self-control can handle the horrible sight of a Medusan (and then only with eye protection). Attempting to kill Kollos, Marvick (jealous of Miranda’s interest in Kollos) goes insane at the sight of the Mudasan ambassador. Before dying Marvick, one of the designers of the Enterprise, takes the ship outside the galaxy where it is hopelessly lost. Once it is discovered that Miranda is blind (she had fooled them with a complicated neural sensor in her dress) and cannot guide the Enterprise, Spock mind-melds with the navigationally proficient ambassador who quickly gets the Enterprise back in known galactic space. However, while severing the mind-meld, he forgets the visor, sees Kollos, and goes insane. Because of her jealousy of Spock’s relationship with Kollos, Miranda hesitates to give help, but with Kirk’s urging reconsiders and helps Spock take control of his mind.