Young Sam Morgan, the Pennsylvania runaway and now a seasoned Rocky Mountain trapper, joins a brigade led by Jedediah Smith, greatest mountain man of them all, heading west for the Mexican province of Alta California. With Sam on this dangerous mission into unexplored territory are his beloved Crow wife Meadowlark and a polyglot host of multi-national fur hunters, Ute and Shoshone Indians. The journey south to the Colorado River and across the Mojave Desert is game rare or nonexistent, water a rarity, strange bands of naked Indians, the hammering sun, all in a godforsaken land of sand and scrub. Sam Morgan's life changed unalterably when the pregnant Meadowlark falls ill as the brigade makes its way through Mojave country. In an emergency push west he is able to bring her safely into the California coastal town of Monterey but there faces the greatest crisis of his life - the death of the only woman he has ever loved.