A gorilla escapes from its master on a ship, breaks into a young woman's home, and kills her. The woman's fiancé, Jim, who had visited earlier, is framed for the murder by the police. The famous detective Sherlock Holmes reads about the case, investigates, and uses his deductive reasoning (playing the violin, finding the gorilla). Holmes exposes the real killer (the gorilla and its master) and frees Jim just before he's convicted, revealing the true sequence of events in court.