Snowfall features another sharp-tongued, uncompromising heroine, Catania Olsen. She is the doctor for and spiritual guardian of a band of hunters who live at the edge of a great Wall of ice in what was once Colorado. In the country of the Trappers, books are hand-copied so that knowledge may be preserved, but the technology described in their precious pages is mostly lost to their fur-clad readers, despite Catania's attempts at scientific treatment and the Trappers' careful husbanding of ancient metal tools.
As a resurgent population moves west and north from the more settled places that had once been the Eastern Seaboard and Gulf Coast of the United States, they drive tribesmen-Cree, Arapaho, and more-before them. On the run and desperate to find new homes, the tribes slaughter entire populations to claim their lands. The Trappers are innocent of this until Jack Monroe, banished years before for murdering a fellow Trapper, arrives, urging them to flee their ancestral home, the Trappers do not listen until nearly too late, until the first enemy arrows have found their marks.
The southern flight of the surviving Trappers is a journey through time as well as space. From a frozen northland where summer lasts two chilly weeks through a burgeoning forest where the Trappers taste their first beef to a gulf coast where warm breezes carry exotic scents and sounds; from a primitive life of hunting and trapping to the luxurious Gardens, where people can still weave and make paper, to a bustling trade mart where man-beasts created by unnatural science tread the dirt streets, Catania is shocked to recognize that the proud Trappers have spent generations clinging to civilization with their fingernails.
The journey into the warm lands will change Doctor Catania Olsen, mind, heart, and soul. She will gain and lose a love, see great wisdom and greater folly, witness amazing miracles and terrifying science, and, most surprising to herself, become a mother. Finally, she will have to choose between her people and her freedom.