Dr. Dudley Duprez is a well-known Louisiana physician. His beautiful but wayward niece, Rose Duprez, is abducted by Paul Crenshaw, a friend of the doctor, and to prevent her shame from becoming known, Rose kills herself. Dr. Duprez learns her secret and determines to make Crenshaw expiate his crime. While traveling on a Mississippi River steamer, the doctor wins Mercedes, a beautiful slave, at cards. He takes her home and, passing her off as a distant relative, arranges it so that Crenshaw falls in love with the girl.