Christopher McDougall, a journalist and running enthusiast, sets out in search of a legendary tribe of tireless runners who live within the massive Copper Canyon of Mexico. The Tarahumara Indians reportedly can run for hundreds of miles without wearing down, and switch instantly to sprint mode to chase down a deer if necessary. McDougall struggles through miles of wilderness to find the reclusive Tarahumara, and is surprised to find a mysterious outsider named Caballo Blanco, or "white horse," living among them. As McDougall trains with the Indians and learns their ancient secrets of health and endurance, he achieves a sense of enlightenment which will completely alter his perspective on running and every other form of motion. To celebrate his newfound spirituality and stamina, he organizes a grueling 50-mile race between members of the Tarahumara tribe and an eclectic mix of distance champions from the United States.

McDougall reveals the secrets of the world's greatest distance runners--the Tarahumara Indians of Copper Canyon, Mexico--and how he trained for the challenge of a lifetime: a fifty-mile race through the heart of Tarahumara country pitting the tribe against an odd band of super-athletic Americans.