For 20,000 miles, Peter Matthiessen crisscrossed the South American wilderness, traveling from the Amazonian rain forests to Machu Picchu high in the Andes, down to the edge of the world at Tierra del Fuego and back. In the course of his journey he followed the trails of old explorers, encountered river bandits, wild tribesmen, and the evidence of ancient ruins, and discovered a fossilized snout of a giant unknown crocodilian hidden in the depths of the jungle on the wild mountain rivers of Peru.