The Vulcan Changeling Project

Doctor McCoy and Spock are searching for a birthday present for James T. Kirk. However they both find more than they bargained for when Spock buys a human slave girl, for she telepathically screams to Spock for help. The method she uses is not supposed to be know to Vulcan offworlders. Together Spock and Kirk must unravel the mysteries of her past and as they do they discover something evil in Vulcan's past.