Constance Hillier and her boyfriend, Thomas Mogson, are convicted of the murder of her aunt, and both are hanged. Before his death, Thomas unsuccessfully tries to save himself by accusing Constance's sister, Margaret, of the crime. Inspector Cleveland of Scotland Yard is faced with a terrible dilemma: either Constance was innocent, or Margaret is being unjustly accused. Either way, Cleveland's career as a policeman appears to be doomed!