In 1917, Madeline Fairbanks is an herbalist healer devoted to the people of Jamesville, a dying town in the Southern Appalachians. Renetta Morgan—with whom it is taboo to fraternize because of race—is her apprentice. Maddie's precocious granddaughter, Hannah Tillman, is mesmerized by an ancestral box in Maddie's possession that contains hints of a mystical heritage.

On a cold September wind, charismatic Carl Howard blows into town astraddle a stallion of near-mythic proportions. With no reason to doubt him, the town accepts him as their new pastor. But Carl casts a wider net, claiming power, leadership, and much more than he has a right to. He fans fear into hatred, leading to racial conflict and oppression of women.

Maddie does not bend the knee to Carl, but continues in her progressive ways—and in doing so, finds herself accused of witchcraft and targeted by the KKK.