Dr. Arthur Conan Doyle assists a young woman, Miss Grace, who is terrified by an apparition that follows her when she bicycles home along a lonely stretch of road. He informs his colleague and mentor, Dr. Joseph Bell who joins him in investigating the case. She believes she is being followed by the spirit of the man who killed her parents some years before, but Bell assures her that the killer was hanged long ago and there has to be another explanation. There are many suspects, including former suitors, an uncle who will soon lose control over Miss Grace's finances and her present fiancée. When Miss Grace is kidnapped, Bell realizes that someone from her past is implicated. He also concludes however that Miss Grace has another dark secret.