As Mrs. Churchill, carrying her pet dog, emerges from Marsden's jewelry shop, Fourteen-Carat Tommy steals her handbag. Although the act was seen by Jean and her assistant, Warrington, Mrs. Churchill denies having being robbed. Mystified, the detectives shadow Tommy and Mrs. Churchill. They see Tommy meet the woman and get into her automobile. Convinced that something is amiss, Jean and Warrington follow. Tommy alights when the auto reaches a house in the suburbs. While Jean endeavors to get into the building, Warrington follows Mrs. Churchill to her home. Tommy becomes aware of Jean's presence. Aided by Jones, a pal, he makes her a prisoner. Warrington enters Mrs. Churchill's home and confronts her. The man discovers that the dainty little coat worn by Mrs. Churchill's dog contains a large quantity of stolen jewelry and that the woman is a member of a gang of jewel thieves. Warrington incautiously steps on a rug in the center of Mrs. Churchill's library. The next instant, the detective tumbles into a cell under the house. To his horror, he discovers that the cell is being flooded. Rats of tremendous size leave their holes to attack him. Warrington becomes crazed with fear. Mrs. Churchill 'phones Tommy and Jones of how she has trapped the detective. The crooks jeeringly inform Jean of her assistant's fate. In desperation, the Girl Detective snatches a pistol from Jones' pocket and shoots, wounding both men. The shots bring officers to the scene. Jean's story causes them to hasten to Mrs. Churchill's home. The woman is placed under arrest. Warrington is saved just as he is about to die.