Suzanne Morse, a midwife in Watertown, moves to a remote frontier town with her husband and two children in 1666. A hands-on, practical woman who needs people, she bonds with the first two women she meets.

The minister's new wife, Abigail Willard, wants to learn Suzanne's trade. At the same time, Dancing Light, a renowned medicine woman in the Nashaway town across the river, calls her to heal her sister, dying of a white man's disease, with white medicine.

In no time, Suzanne becomes known as an effective healer among Groton settlers, and Reverend Willard certifies her, a necessity to practice in the Puritan colony. However, the friendship between Suzanne and Dancing Light—the two collaborate—arouses the town's approbation.

Abigail, too, is compromised when her servant, sixteen-year-old Elizabeth Knapp, is "bedeviled," famously accused of being a witch. Some villagers project their fears on the neighboring natives, as well as anyone who befriends Suzanne, a friend of the witch doctor. Despite her successful practice, birthing four more children, and two sisters marrying and moving to Groton, Suzanne must warily handle the rising tension in her community. It comes to a head in 1676 when King Philip's War reaches their small settlement, and in the heat of a siege, her neighbors turn on her.