January 1814 in the Boise River country of what is now southwestern Idaho.

A Shoshone person comes to the base camp with a warning.

The Bannock are going to attack.

Marie makes a decision.

She does not run west.

She does not take the easiest path to safety.

She loads her sons onto a horse, gathers supplies, and rides east toward Pierre’s camp, three days away through the winter mountains.

The quality of that decision — to ride toward danger in order to warn someone she loves — is the human core of a story that is also a story about geography, history, economy, and the intersection of cultural worlds.