Deep in the heart of Oregon County, one young woman will fight to keep her family safe.
Grace Martindale has endured more than her share of hardship. After her parents passed away, she raised her two younger sisters, Hope and Mercy. Moving to the West seemed like an opportunity for a fresh start, but it left Grace in a precarious position instead. Missionary Dr. Marcus Whitman and his wife agree to let Grace and her sisters stay at their mission for the winter. The three sisters are united in gracious hospitality and have nowhere else to go until they hear from their uncle in Oregon City.
While Grace is busy adjusting to life in the Wet, she meets a fur trapper named Alex Armistead who equally intrigues and infuriates her. When a measles outbreak threatens lives at the mission and among the native Cayuse who live nearby, it is Alex who helps Grace use the natural healing remedies she learned from her mother to help where she can, despite Dr. Whitman's disapproval. As the death toll rises, so do tensions between the settlers and the natives, and Grace soon finds herself and those she loves in more danger than she imagined possible.