Amy, Christine Taylor is an elementary school teacher who is haunted by nightmares about doctors and hospitals, a shadow of the circumstances surrounding her father’s death. On the afternoon that her fiancé Nick Shane Brolly proposed, the two are swept into a serious car crash. An ambulance carries Nick away without ever revealing which hospital he’s headed to. Amy and Lucas, Jerry O'Connell the driver of the other vehicle, set out to locate where Nick and Lucas’s sister have been taken, clinging to fragments of hope as Amy’s grip on reality begins to fray and she spots disfigured faces, even her own reflection, in a mirror.
A frightened little girl from Amy’s class, Melissa Chloë Grace Moretz, steps forward with a strange offer of help, claiming she can guide Amy to Nick and naming a place: St. Rosemary’s Hospital. This clue drives them toward a chilling history: St. Rosemary’s was once rumored to be the home of devil worshipers, and it burned down nearly seven decades ago, taking with it all the nurses and staff who refused to leave. At the hospital, Nurse Holiday Mary Pat Gleason and others there enact a nightmarish tableau—blood is sprayed, a patient is consumed, and a hallway seems to loop back on itself—while Nick endures his own macabre trials behind closed doors, all echoing the same cursed place Amy is chasing.
As another terrifying vision crashes over her, Lucas consoles Amy only to reveal himself as something far more sinister: a demon who taunts her about her father’s death and the life she thinks she’s losing. She slips away, hailing a cab to return to the hospital, where she fights through a gauntlet of nurses and hallucinations of dead patients. In a haunting confrontation, she encounters the ghost of her father and replays the moment from when she was twelve, a moment when, at his insistence, she unplugged the machine keeping him alive. The revelation is devastating, and the Lucas demon closes in, telling Amy that she belongs with the ghosts and monsters of St. Rosemary’s because she murdered her father.
Driven by a surge of resolve, she scorches the demon with scalding steam and manages to slip free, finally pulling Nick away from the operating table. The hospital itself seems to ignite, flames licking the corridors as they race toward the exit and stumble into the bright light beyond. When Amy wakes, she finds herself still tethered to the car crash that started everything, and the visions she endured begin to feel like a test—one that leaves her teetering on the edge of life and death, as the border between wakefulness and the other world grows dangerously thin.
