The House Without a Key (1926)

A Pathe serial in ten chapters of two-reels each: Dan Winterslip, a wealthy man in Honolulu, has not spoken to his brother, who owns a hotel next to Winterslip's estate, in over twenty years. Minerva, sister to the estranged brothers, comes from Boston to try to reconcile the two men. John Quincy Winterslip, Dan's nephew, receives a letter instructing him to retrieve a box from an attic in San Francisco and dump the contents into the ocean. He is on board a ship bound for Hawaii in which other passengers are also after the box. Dan Winterslip is murdered. Charlie Chan, a Chinese detective, offers to help solve the killing and the mysteries surround the box. Chan is looking for the person whose wristwatch is missing the number 'three.'