During the winter of 1825, Richard Hamilton--a timid Harvard philosophy student--arrives in St. Louis on business for his father. Robbed and beaten, desperate to save his life, he reluctantly joins the crew of the Maria, a fur trader's keelboat. Bound for the beautiful, wild, and dangerous Indian country of the Upper Yellowstone River, the native Bostonian begins the education and adventure of a lifetime.

On a converging path is Packrat, a Pawnee warrior who captures a beautiful young Shoshone medicine woman named Heals Like a Willow. But slaves with ties to the spirit world can--and do--fight back.

As the Maria struggles deeper into the wilderness, Richard and Willow are cast together: seekers of knowledge and spirit, unwitting adversaries separated by time, space, and birthright. As inevitable as the collision of their two worlds, their love begins to unfold--and with it the terrible consequences of a forbidden consummation.