Grace Rhodes, Naomi Watts, returns to Grand Island, Nebraska, to care for her agoraphobic mother, June Rhodes, [Karen Black], who refuses to leave her yard. She also looks after her younger siblings, James Rhodes, [Mark Salling], and Margaret Rhodes, [Jamie Renée Smith], and takes a job again at Dr. Larson's local clinic, where William Windom portrays Dr. Larson. The family’s quiet routine is shaken by the creeping sense that something dark is unfolding just beneath the surface of their town.
As the days pass, James and Margaret fall ill with fevers and symptoms matching those in June’s recurring nightmares. Grace notices that a number of other children in town exhibit the same troubling signs, and at night the fevers surge only to suddenly recede. The illness seems almost malevolent in its timing, a pattern that unsettles Grace and the clinic staff, yet stubbornly refuses to explain itself.
Meanwhile, Donald Atkins, Brent Jennings, and his wife Sandra watch their son Marcus, Lewis Flanagan III, behave strangely. One night, a cluster of children arrives at the Atkins home, led by a child preacher, and Sandra is murdered before Marcus’s eyes. The sheriff, Richard Gross, arrives on the scene, and Marcus tries to flee, but is pursued. The child preacher confronts and kills the sheriff, deepening the town’s fear. Donald, now a suspect in his wife’s murder, hides away with two elderly sisters, Jane Nock, Salle Ellis, and Rosa Nock, Marietta Marich.
The children in town stop answering to their names and insist they are other people. Dr. Larson recognizes the names as those of dead children from the town’s history. In a brutal turn, he is killed in his office by two children, and when Grace returns the next day, his body has vanished. Blood tests in the clinic reveal alarming signs of decay and death, and June’s nightmares begin again—only now they are not dreams but grim, waking events.
Grace pushes forward to uncover the truth, and Donald hijacks her car, forcing her to drive at gunpoint to Jane and Rosa’s house. Rosa explains that the child preacher, Josiah, was the illegitimate son of a local woman who, over the years, was taken in by traveling preachers and granted the power to preach. Josiah stopped aging and remained a boy, a dark secret that the traveling preachers tried to hide by stunting his growth; when word got out, they abandoned him. Josiah killed the preachers, and the townspeople burned him alive, sealing his remains in a well. Mary Anne, Grace’s best friend and co-worker, Samaria Graham, is killed by Josiah, intensifying the peril surrounding Grace and the others.
Back at the clinic, Grace and Donald discover that Margaret is missing, and a chilling revelation emerges: Josiah’s weakness is mercury. The town’s children converge on the barn, offering their blood to Josiah in exchange for life. Marcus, despite being a hemophiliac, sacrifices his own blood, and Margaret offers her soul. Marcus bleeds profusely and collapses; Margaret is pulled into the pool of blood, and Josiah finally rises from the waters of the barn.
Donald and Grace race to the barn, where they connect its sprinkler system to a supply of mercury. Donald loads two bullets with mercury and hands one to Grace. He staunches Marcus’s bleeding, but the other children press their attack. Josiah assaults Grace, who shoots him with the mercury bullet. She discovers the bodies of June and Dr. Larson, and Josiah returns for another strike, only to be met by Grace’s sprinkler system, which showers him in mercury. She finishes him with a brutal slash from his own scythe, and the children, stripped of their venom, return to normal. Grace finds Margaret near the water, nearly drowned, and manages to revive her.
In the end, a shattering truth comes to light: Margaret is Grace’s daughter, whom she had abandoned with June as a teenager. After the victims’ funerals, Grace, Margaret, James, Donald, and Marcus leave Nebraska behind, seeking a life beyond the shadows that haunted their town. The backdrop of Grand Island, once quiet and ordinary, remains a reminder of the cost of confronting buried secrets and the furies that can rise from them.
