Inspired by a true story. In 1825, in a remote Irish valley lying between the mountains and Flesk river of Killarney, three women are brought together by strange and troubling events. Nora Leahy, a widow, has lost her daughter and her husband in the same year, and is now burdened with the care of her grandson, Michael. The boy cannot walk or speak and Nora has kept him hidden from neighbours, who might see in his deformity evidence of supernatural interference. There is rumour that Michael is a changeling, a 'fairy stock', and the cause of the ill luck that swarms the valley. Down by the river, an old woman known as Nance Roche lives alone, acting as a 'doctress' to the community, a person said to possess knowledge from the Good People that enables her to cure inexplicable ills. With the arrival of a new priest and his determination to cleanse the valley of superstitious practices, the purity of Nance's actions is called into question. As misfortune begins to befall Nance's patients and her need to assert her importance to the community intensifies, Nora Leahy brings Michael to be cured.
The women begin to banish the changeling and restore the healthy child, but as their desperation increases, their folkloric practices become more dangerous, until all their lives are in danger.