The Crimson Flame
Franklin W. Dixon
 The plot begins with Frank and Joe witnessing a westerner being attacked by a notorious jewel thief Oscar Tamm. The westerner reveals himself as Alfred McVay and as a avid jewel collector. Due to suspicious happenings at his ranch house in Arizona, he hires the Hardys for protection. Upon reaching there the Hardys start to investigate the strange happenings and develop an immediate dislike of the foreman, Wat Perkins. The are also intrigued by a "mysterious rider" who seems to be sending messages to someone in the ranch house. They also grow suspicious of the butler Wilbur. When a tornado strikes the ranch, the Crimson Flame, a priceless ruby gets stolen. McVay becomes morose and the Hardys, with a couple of clues, pursue the jewel thieves to Thailand. The rest of the plot follows how the boys help capture the crooks and eventually, how the lost ruby is found.