In 1922 London, Sarah Piper is a lonely, impoverished young woman scraping by on sporadic temporary jobs. When her agency sends her to meet a potential employer at a coffeehouse, she finds Alistair Gellis, a charming man in his twenties who researches haunted properties across England. Alistair has found an extraordinary haunting in a tiny village called Waringstoke: At Falmouth House, the ghost of a former servant girl named Maddy Clare, who hanged herself in the barn at 19, has physically attacked a vicar during a failed exorcism. The lady of the house, Mrs. Clare, will allow Alistair to investigate only if he brings a woman to enter the barn, since Maddy feared and hated men in life. Though terrified, Sarah agrees.
During the drive, Alistair tells Sarah he first became fascinated with ghosts as a teenager and describes his equipment, including a camera and a sound recorder normally operated by his assistant, Matthew Ryder, who is temporarily away. They arrive at a quiet country inn, where locals eye them with suspicion.
The next morning, Sarah glimpses Alistair outside the inn with a strikingly beautiful local woman named Evangeline Barry. Their exchange is charged with painful history, deflating Sarah's nascent romantic interest in Alistair. At Falmouth House, Sarah meets Mrs. Macready, the elderly housekeeper, and Mrs. Clare, who is frail and desperate for relief from the haunting. Mrs. Clare insists Alistair leave the property before Maddy senses a male presence and sends Sarah to the barn alone.
Inside, Sarah finds a scene of violent destruction. A stall door swings by itself, bare heels kick rhythmically against the wall behind her, and an inhuman gurgling moan fills the air. The barn appears to erupt in flames, but the fire vanishes instantly, a hallucination projected by the ghost. Sarah flees in shock.
Back at the inn, Matthew Ryder bursts in, having cut short his trip. He is rough, foul-mouthed, and intensely driven, nothing like the quiet intellectual Sarah imagined. Both men are astonished by the haunting's sophistication. Sarah later overhears Matthew urging Alistair to send her home, while Alistair insists her sensitivity makes her ideal for the work. That evening, Sarah accidentally sees Matthew shirtless, revealing an enormous burn scar covering his back and right arm from a war injury. He misreads her shock as revulsion. Alone afterward, Sarah realizes she feels not disgust but powerful attraction.
Lengthy interviews with Mrs. Clare and Mrs. Macready reveal Maddy's full history. Years ago, Maddy appeared on the Clares' doorstep one rainy night, bruised, barely clothed, and unable to speak, bearing signs of severe physical and sexual assault. No one claimed her as missing, and the Clares took her in. Maddy remained terrified of all men and periodically erupted into rages. After seven years, she hanged herself, leaving a note: "I / WILL / KILL / THEM." When Sarah returns to the barn, Maddy grabs her arms with an icy grip, lifts her off the ground, and speaks inside her mind, demanding: "Bring him to me."
The team faces escalating danger. Sarah's room is ransacked by an unknown intruder. Matthew examines the bruises Maddy left on Sarah's arms, which have turned an unnatural chalky white. When the skin is touched, Sarah experiences vivid visions of treetops and a redbrick chimney seen from ground level, images she senses carry desperate urgency. Sarah learns that Tom Barry, Evangeline's domineering husband, is close friends with the church groundskeeper Bill Jarvis and an odd-job man named Roderick Nesbit, who was spotted lurking at Maddy's funeral. Evangeline approaches Sarah privately, desperate to know if the ghost has spoken.
Hundreds of crows gather on and around the barn, and Alistair insists all three enter together. Inside, Maddy manifests differently to each person: Sarah hears footsteps; Matthew sees Maddy hanging from the rafters; Alistair hears music. Maddy speaks in Sarah's mind, gloating that Sarah has delivered Alistair as demanded, and orders Sarah to find the three men who attacked her and her original burial place. Mrs. Clare bursts in and smashes an oil lamp, setting the barn ablaze.
Matthew drags Alistair out, then runs back in for Mrs. Clare and the recorder. Alistair collapses into a dissociative state, believing he is back in the trenches. The crows rise from the burning barn in a black column and fly toward the woods. With Alistair incapacitated, Sarah and Matthew must solve Maddy's mystery alone.
The recorder, though turned off, has captured Maddy's frightened voice saying, "Where am I?" Sarah connects the sounds to her visions and concludes that Maddy is revealing her original burial place, not the churchyard grave. Further interviews yield a critical detail: Maddy's feet were muddy but uninjured when she arrived at Falmouth House, meaning she had not walked far. Matthew reaches the horrifying conclusion that Maddy was buried alive by her attackers, woke in a shallow grave, clawed free, and ran.
As Alistair deteriorates, Sarah and Matthew draw closer. Matthew tells Sarah how he received his scars: His unit sheltered in a barn in France that was bombed, and he survived by running out burning and rolling in mud. Sarah confides that in 1919, her father died of influenza and her mother drowned herself while Sarah was away. An anonymous benefactor, later revealed to be Evangeline, hires a nurse for Alistair and pays the inn's bills. Evangeline also confides that Alistair proposed to her in 1914, before learning she was already married to Tom. Maddy appears to Sarah at night, implying she has killed Jarvis and will return Alistair only if Sarah finds the burial place.
Jarvis disappears, his shotgun found dropped in the weeds near the woods. The constable orders Sarah and Matthew not to leave town. They split up anyway. Sarah goes to Nesbit, who confesses: He, Jarvis, and Tom Barry found Maddy walking through the woods in 1914. Led by Barry, they raped and strangled her and buried her near the well behind Barry's house. Barry rebuilt his chimney five years ago; the old one was redbrick, confirming Sarah's visions.
Sarah races to the Barry estate, realizing Matthew is in danger. She finds the overgrown depression near the well that matches her visions. Tom Barry appears behind her with a rifle, having already knocked Matthew unconscious. He locks Sarah in the cellar. From below, she hears hundreds of crows descend on the house, beating against every window. She screams warnings about Maddy, but Barry goes upstairs. Crashes, a dragging sound, one shout, then silence. Barry never speaks again.
Constable Moores, summoned by Evangeline, releases Sarah from the cellar. Matthew is alive but badly injured. Barry is found drowned at the river's edge with drag marks from the house but no marks on his body. Jarvis has been found dead of a seizure; Nesbit has shot himself. As Sarah sits with Matthew's head in her lap and tells him she loves him, she senses Maddy behind her.
For the first time, Sarah sees Maddy clearly: a translucent young woman in a cheap blouse and bolero jacket, her best clothes, worn the day she set out looking for work. "I didn't want to," Maddy says. "I'm so tired." Sarah tells her to go. Maddy walks toward the woods, her hair lifting in the breeze, and disappears. Constable Moores passes within inches of her without seeing a thing.
Alistair recovers, freed from Maddy's hold, and decides to stop ghost hunting. He and Evangeline plan to try life together. Alistair tells Sarah that Matthew loves her, though Matthew struggles to express it. When Matthew asks Sarah to come meet his parents, she accepts, and they leave Waringstoke together.