It's 1956, and Lee Plunkett has taken over the family business as a private investigator despite his reluctance to follow in his father's footsteps. When murder intrudes on a group of ghost seekers, Lee is asked to solve the case by a cop on the verge of retirement. At the urging of his perpetual fiance Audrey, Lee enlists the help of Mr. O'Nelligan, a scholarly Irishman with a keen eye for solving mysteries. The duo is drawn into a murder investigation...