LEWIS, indentured to the scullery of a large Boston hotel, has always dreamed of seeing the world… or at least something beyond the grim stone walls that have imprisoned him since birth. Entranced by the adventures of JOHN C. FREMONT, the Pathfinder who famously charted America’s route to the West, he has religiously hoarded every word — by or about the man — in the newspapers that come down to the basement as trash; and has taught himself map-making as a way of emulating his hero to some extent.

When Fremont happens to spend a night at Lewis’ hotel, the boy manages to get his work included with the breakfast tray. Impressed and desperately in need of new blood, Fremont recruits Lewis for his Fifth Expedition. Fremont’s brilliant reputation has been marred by the disaster of his previous expedition, when a third of his party died of starvation and cold in the mountains. Now he is determined to redeem himself by proving that his chosen 38th parallel is in fact the optimal route for a national railroad.

As Lewis patiently absorbs lessons in astronomy, geometry and the basic human intercourse that has been denied him until now, a ragtag group of daguerreotypists, artists, hunters and muleteers is assembled. Lewis finds himself thrillingly launched into the vast openness of the Missouri River and the Kansas plains beyond.

Slowly however he becomes convinced that Fremont is leading the expedition into disaster. He is intent on proving a route for the railroad where no railroad can go. It will be up to Lewis alone to save his companions. But surrounded by hostile Indians, scorching deserts and snow-bound mountains, can he even save himself?

ADELINE CARSON’s story unspools simultaneous with Lewis’ and is told in alternating chapters. The half-breed daughter of Kit Carson and his Arapaho wife, Addie lost her mother when she was only three; and lost everything else at five, when she was abandoned for almost a decade in an all-white convent school. Finally brought back to Taos by her beloved father, she married the closest thing to him she could find: LOUY SIMMONS, a taciturn trapper three times her age. Almost immediately, however, she finds herself smitten by GEORGE STILTS, a travelling fiddler. The infatuation is mutual. Trapped in snow-bound Taos, the two begin a dangerous relationship. Everyone in town knows what’s going on and everyone knows that Simmons is vengeful and a dead shot. The two prepare to flee… until Stilt learns that Addie is pregnant. He will not risk her or their unborn child. Fortuitously, Simmons and Carson have been preparing to drive sheep to the Gold Rush country to make quick money. Stilts sends Addie with them, fakes his death in the northern passes and heads south to take the Gila River route to California.

But surrounded by men and sheep and yet totally alone, Adeline miscarries her baby. By the time she is reunited with Stilts – who has found peace as a shopkeeper –, she has decided that the emptiness within her is more than physical. She has to walk east to her mother’s lands to find the self she lost.

Thus Lewis and Adeline are set on a continent-long trajectory toward each other. Between them lies a newly forged America seething with seduction, betrayal, casual violence and most savage nature. But stronger than any of these is love.