Still stinging from his recent election loss, former president Theodore Roosevelt sought refuge in the Brazilian jungles in early 1914 on an expedition to trace the last unmapped Amazonian river system, the Rio da Dúvida or The River of Doubt. Co-commanded by famed Brazilian explorer Colonel Candido Rondon and staffed with Roosevelt’s 24-year-old son Kermit, naturalist George Cherrie, and more than a dozen local porters and laborers, the Roosevelt-Rondon Scientific Expedition was plagued by disaster from its very onset—incompetent planning and inadequate outfitting would result in near mutiny, hunger, death, and even cold-blooded murder. But Roosevelt meets an odd stranger along his ill-fated journey, who tells an astonishing tale that could challenge the very core of modern Natural History. Weakened by illness and starvation, Teddy Roosevelt is caught in a web of unfathomable danger, the results of which would alter his life and the lives of his companions forever.