Set in a remote valley in County Kerry, Ireland, in 1825, the story follows three women whose lives converge around a disabled child in a community steeped in folk belief. The valley is an insular world of subsistence farmers where Catholic faith mingles with older traditions: belief in the Good People (fairies), herbal cures, and keening, the traditional Irish practice of ritual wailing for the dead.
When Martin Leahy dies suddenly at a crossroads, his wife Nóra receives the body in shock. Before neighbors arrive for the wake, she sends away her four-year-old grandson Micheál, who lives with them. The boy cannot walk, speak, or sit up on his own, and Nóra does not want anyone to see him. Nance Roche, an elderly healer who lives alone in a mud cabin near a fairy fort, arrives uninvited to lead the keening, claiming she foresaw the death. Father Healy, the parish priest, reluctantly says prayers and condemns Nance's practices as heathen.
Micheál was brought to Nóra and Martin the previous harvest by his father Tadgh, after Nóra's daughter Johanna died of a wasting sickness. The boy arrived half-starved and has deteriorated into a state of rigid limbs, vacant staring, and constant screaming. Nóra's neighbor Peg O'Shea is shocked and speculates behind Nóra's back that something is deeply wrong. Now alone with the boy, Nóra is overwhelmed and ashamed.
On Peg's advice, Nóra hires Mary Clifford, a fourteen-year-old girl from Annamore, at the November fair in Killarney. Mary is alarmed when she first sees Micheál. She settles into a routine of milking, tending hens, and enduring broken nights of the boy's screaming.
When Tadgh visits, he reveals that in Johanna's final days she did not recognize Micheál and screamed for him to be removed. Mary, overhearing, blurts out that Micheál is a changeling, a fairy child swapped for a human one, and that everyone in the valley knows it. At the well, Kate Lynch and her sister Éilís O'Hare warn Mary that the boy has brought misfortune to the valley.
Nóra seeks help from Father Healy, who dismisses Micheál as an "idiot" and refuses to engage with talk of fairies. In desperation, she whips the boy's legs with nettles, hoping to restore feeling. Mary runs for help and encounters Nance, who learns Nóra is hurting the child. Nance examines Micheál, finds his legs unevenly grown, and pronounces him fairy-touched. Nóra confesses she cannot love the child and is convinced he is not her grandson. Nance agrees to attempt cures to restore the real Micheál.
Nance's backstory emerges through memories. She believes her mother was "swept" by the fairies, and her aunt, Mad Maggie, taught young Nance herbal medicine and the ways of the fairy world. After her father drowned and Maggie vanished, Nance spent years on the roads before settling in the valley.
On New Year's Eve, Nóra and Mary bring Micheál to Nance's cabin. Nance pours mint juice into the boy's ears and rubs selfheal into his feet. The next morning he is unchanged, confirming to Nance that the child is a changeling.
Tragedy strikes when Daniel Lynch, Nóra's nephew, fetches Nance after Daniel's pregnant wife Brigid goes into labor. The baby is born dead. Kate Lynch spreads rumors that bittersweet berries Nance gave Daniel poisoned the child. Daniel buries the coffin alone in the
cillín, unconsecrated ground for unbaptized infants.
When Nóra demands a stronger remedy, Nance prepares a bath of foxglove, known as
lus mór, a poisonous plant associated with the fairies. Mary and Nóra immerse Micheál in the water and squeeze foxglove juice onto his tongue. The boy convulses violently, and the women swing him through the doorway on a shovel, chanting, "If you're a fairy, away with you!" He vomits for days but returns to his previous state.
Tensions against Nance escalate. Áine O'Donoghue, the childless blacksmith's wife, catches fire while heating a remedy Nance prescribed. Father Healy and Seán Lynch, Kate's violent husband, drag Nance from Áine's bedside and throw her into the mud. A
piseóg, a malicious charm of woven straw and rotting blood, is found on Seán's land, and Seán leads men to threaten Nance at her cabin. Father Healy accuses Nance of cursing the valley.
Nóra presses for a final cure. Nance refuses fire, recalling her aunt Maggie's scarred face, and instead proposes bathing Micheál in boundary water, the confluence of three streams in the river Flesk, for three consecutive mornings before sunrise, with all three women fasting.
The first two mornings, Mary and then Nóra carry the boy into the freezing river and submerge him three times each. On the third morning, Mary resists handing the boy over. Nóra slaps her and takes him. Nance, naked in the current, submerges the child three times while Nóra holds his chest and Mary weeps on the bank. The boy's struggles stop. When Nance lifts him from the water, he is not breathing. Nóra, seeing yellow iris on the bank, runs home convinced the fairy has departed and Micheál will be waiting. Mary flees in horror.
Mary raises the alarm at Peg's cabin, and police from the Killarney barracks arrest all three women. Nance leads them to the Piper's Grave, a fairy fort marked by a whitethorn tree, where she buried the body. The coroner charges all three with wilful murder, and the case proceeds to the Summer Assizes in Tralee. Father Healy arranges for Mary to testify as the Crown's chief witness in exchange for the charges against her being dropped.
Nóra and Nance endure months in Ballymullen gaol. At trial, Mary testifies to the nettling, the foxglove, and the three mornings at the river but states she did not believe the women intended to kill the child. Nóra insists she wanted her true grandson back. Nance testifies about the Good People and her belief that the child was fairy; the court regards her with pity and disdain. The defense argues the drowning resulted from superstitious belief, not murderous intent. After less than 30 minutes, the jury returns a verdict of not guilty.
Mary, watching from the crowd, spits and mouths, "I curse you," before disappearing. She decides not to return home and stands in a Tralee street positioning herself for hire, haunted by the smell of Micheál still on her clothes.
Nóra returns to the valley to find her cabin lost for unpaid rent. She searches it for the restored Micheál but finds only a brooding hen on her bed and realizes the boy has not been returned. Peg tells her Micheál was buried in the
cillín and that the valley's milk and butter have returned since his death. Nóra must move in with Daniel and Brigid, stripped of her home and her hope.
Nance walks four days from Tralee to find her cabin burnt to ashes by Seán Lynch and the valley men. Peter O'Connor, the local ploughman and one of Nance's few defenders, finds her in the warm ruins at dawn; he had rescued her goat before the fire. Peter takes Nance to his cabin and offers to marry her so she cannot be driven out. Before dawn the next morning, Nance milks the goat, leaves the milk and a dead ember on Peter's dresser as a blessing, and walks alone into the early-morning light.