In 1869, ten explorers set off to chart the Green and Colorado Rivers, under the guidance of John Wesley Powell, a one-armed, Civil War veteran and personal friend of President Grant; a government-sanctioned journey following in the footsteps of the deserters, lone adventurers, and countless indigenous people who have previously braved the wild rapids leading through Colorado, Utah, and New Mexico, and through the most dangerous waterway of all: the Grand Canyon. Along the way, they make friends. They get on each other’s nerves. They suffer loss of boat and supplies. They doubt, struggle, name mountains after themselves. They posture and pretend. They quit while they’re ahead and they repeatedly brave dangerous rapids to reach the other side. As boats capsize and supplies are lost, as belts tighten and nerves fray, the company draws together as a band of brothers, even as three members f...