Mrs. Wethersby comes to the station with the complaint that several thefts have been committed in her house, and Kate Kirby, a detective, is allowed to undertake the investigation as her first case. Accordingly she eaters Mrs. Wethersby’s house as her private secretary. She subjects the inmates of the house to a severe scrutiny. Besides Mrs. Wethersby, the household consists of a dissipated son and three servants of suspicious appearance. While writing invitations to a house party in Mrs. Wethersby’s room. Miss Kirby discovers a revolver in the drawer of the desk, which Mrs. Wethersby explains she keeps on hand for protection. An inspection of the desk and the wall of the room causes a peculiar expression to pass across Miss Kirby’s face. With the aid of a piece of chewing gum, she takes an impression of the key to Mrs. Wethersby’s room, and has a duplicate key made for herself. The guests arrive at the house party and go to their rooms to dress for dinner. Miss Kirby, sitting at Mrs. Wethersby’s desk as the hostess makes her preparations, is aware of a subtle delicate perfume, which is markedly different from the odor of the cologne with which Mrs. Wethersby is liberally spraying herself. Immediately the girl’s suspicions are confirmed, and she sends immediate instructions to the police. That night after the guests have retired, Miss Kirby steals along the dimly lighted hall, and listens with her ear against the wall outside Mrs. Wethersby’s room. Suddenly she glides to the door, unlocks it with her duplicate key, and enters. Taking the revolver from the drawer of the desk, she waits quietly. After a few moments, the wall of the room slides out of place without a sound, and Mrs. Wethersby, herself the thief, enters through the secret panel, carrying the jewel boxes of the young heiress, whose room is next to hers. Confronted by the quiet figure of her secretary, Mrs. Wethersby rushes to the desk drawer. The discovery that the revolver is missing leaves her no other alternative than to await the arrival of the police, who quickly answer the young detective’s signal.