When Nancy Drew, together with her two close friends, arrive for the Emerson University June Week celebration and learn there has been a mix-up in their motel reservations, the confusion leads to a baffling mystery. Uncle John Rorick, a descendant of the early settlers of the town of Emerson, invites the three girls to be his guests at his historic mansion on Pine Hill. Shortly after their arrival, he tells them about the phantom who haunts the mansion's library.