A man is found murdered in a locked Manhattan apartment, the only other inhabitants of which were his niece and a servant. The niece, under suspicion, will be indicted unless Otis Landon, a young lawyer from the apartment across the hall can discover the real killer. The clues, a safety deposit key, a woman's hat pin without a head, a railroad timetable, and two music hall tickets, each point to a different person, none of whom can have committed the crime. From these clues, Landon, with the help of the noted detective, Fleming Stone, must forge the chain of evidence with which he can convict the killer and prove the innocence of the niece.