"Guard this letter as you would your life!" With these words ringing in his ears, Biff Brewster boards the Brazil-bound plane to join his father on a safari to the headwaters of the Amazon River-a safari that, to Biff's amazement, becomes a deadly contest for fabulous riches. From the beginning, Biff, his father, Biff's friend Kamuka, and the rest of the party find their path menaced by an enemy who never reveals himself. Is it Nicholas Serbot, the suave stranger whom Biff first meets on the plane? Or is it Joe Nara, the eccentric old prospector, the only white man alive who knows the route to the almost legendary El Dorado gold mine? Biff and Kamuka find their days crowded with the hazards and thrills of jungle travel as they trek through a wilderness echoing with the threat of "Macu"-the dreaded headhunters. And waiting for them at the end of the trail are a shock and a surprise beyond their wildest dreams. "Andy Adams" was a house name used by Grosset & Dunlap for their "Biff Brewster Mystery Adventure" series. Walter B. Gibson, famous author of The Shadow novels, wrote and/or co-wrote 5 books in the series including "Brazilian Gold Mine Mystery."