Roosevelt's Beast

1914. Brazil's Rio da Duvida, the River of Doubt. Plagued by hunger and suffering the lingering effects of malaria, Theodore Roosevelt, his son Kermit, and the other members of the now-ravaged Roosevelt-Rondon scientific expedition are traveling deeper and deeper into the jungle. When Kermit and Teddy are kidnapped by a never-before-seen Amazonian tribe, the great hunters are asked one thing in exchange for their freedom: find and kill a beast that leaves no tracks and that no member of the tribe has ever seen. But what are the origins of this beast, and how do they escape its brutal wrath?