In 1819, Bet Hex ventures up the Missouri River with a fur-trading expedition. Captured first by Arapahos and then by Pawnees, she is rescued by a French voyageur. After his death, she sets out to make her home in the wilderness. The Blackfeet call her "White Woman Who Never Dies" and she lives up to that name, surviving wildfires, harsh winters, and the dangers of animal and human predators. She befriends a Salish man, raises a little girl, and deals with Blackfeet raiders and Black Robe missionaries. She would rather swim with beavers than kill them and rather love a man than fight him, but Bet Hex does what she must to survive as the one and only mountain woman.