Sherlock Holmes and Dr. Watson are going on a fishing trip, and while they are riding the train, they meet Watson's old friend Reggie Taunton. Taunton asks Holmes if the detective would mind helping him with an odd problem. Taunton's archaeologist uncle has sent him an authentic Egyptian mummy, and strange laughing sounds have been coming periodically from the sarcophagus. Holmes visits Taunton's home, and has dinner with Reggie, Reggie's fiancée, the fiancée's aunt, and an Egyptologist who knows Reggie's uncle. While they are dining, the mummy starts to make the noise, and Holmes quickly finds a very simple explanation for it. But in the course of examining the mummy and the sarcophagus, Holmes uncovers a more serious mystery.