Helen Delaine, a noted woman detective, is assigned to run down a gang of robbers. She trails "Diamond" Flora and Eddie "Frisco" Martin, two of its members, to a Canadian hotel. Posing as Ruth Dayton, an heiress, she gets acquainted with the crooks and invites them to visit her. Flora and Eddie arrive at the Dayton home, and there Helen, with the aid of Jack Delaine, her husband, lay their trap. They show the crooks the safe where "Ruth" keeps her jewels, and even give them the combination. That night Helen and Jack hide in the vault room. Flora and Eddie appear after midnight and blow open the safe's door. Out step the detective and her husband with drawn revolvers. A fight ensues but the crooks finally are overpowered.
—Moving Picture World synopsis