In 1912, twenty-two-year-old Evelyn Grace leaves New York after attending a Christian revival where she learns about a mountain mission in the isolated Appalachian village of Asher, Tennessee. Idealistic, educated, and quietly determined, she arrives believing she has come to teach poor children and serve God. Instead, she enters a world shaped by hardship, folk medicine, clan loyalties, suspicion of outsiders, moonshining, and deep spiritual hunger.

At the mission, Evelyn is taken under the care of Temperance Pinkham, an older Quaker woman who speaks with plain, old-fashioned wisdom and believes the people of Asher do not need to be "fixed" so much as understood. Evelyn also comes into conflict with Reverend Jeremiah Grigs, a stern old-school minister whose views on women, education, and modern thinking clash with her own. Meanwhile, she forms a life-changing friendship with Anna Rowntree, an Appalachian woman hungry to learn to read, and slowly becomes aware of Dr. Henry Farlow, a mountain-born physician whose cold reserve masks a divided soul.

As Evelyn begins teaching, she discovers that children are being pulled from school to work for Joseph Ruths, a violent moonshiner who uses his son Horace to recruit boys into the trade. What begins as a mission of service becomes a test of courage, faith, and endurance.