Early in "Fiery Eye," Gus reveals that a mysterious gentleman with three dots on his forehead once came to his home and tried to inquire the location of Gus's uncle, Horatio August/Harry Weston in connection with something called The Fiery Eye. That memory gives Jupiter the clue to realize that Gus's inheritance is most likely a jewel of immense value. As it turned out, Gus's uncle had obtained the Fiery Eye from a temple official at the Temple of Justice in Pleshiwar, India. The temple official feared that the Fiery Eye would reveal his guilt in an incident (The Fiery Eye was rumored to glow brightly when in the presence of a guilty individual).
Three Dots came to the U.S. after discovering that Gus's uncle had died. He assembled a gang of criminals who wore horn-rimmed glasses and false mustaches to try to obtain the Eye before the boys could find it. Three Dots had a unique weapon that he used to threaten the boys on several occasions--a walking cane with a concealed sword inside. To scare the boys, he pretended once in the story to have killed Hugo, one of his gang who had obtained the paste imitation of the Fiery Eye from the broken bust of Augustus.
After the boys found the Eye and escaped from his gang, Three Dots finally realized that he couldn't frighten them into giving him the Fiery Eye without incurring the wrath of the Fiery Eye itself. Therefore, he paid Gus a handsome fortune and returned the Eye to its rightful place at the Temple of Justice.