When a landlady finds one of her tenants murdered, Inspector Hornleigh is sent to investigate. Inspector Hornleigh's assistant, Sergeant Bingham, soon finds an attaché case that had been stolen from the murdered man. When Hornleigh examines the case, inside it he finds a bag that was used to carry important government documents. The documents have been taken, and to make things even more confusing, a duplicate of the stolen bag soon turns up.