Graduate student Mia Medina chooses Alzheimer’s disease as the subject for her documentary, securing permission to film the daily lives of Deborah Logan and her devoted daughter, Sarah, at their secluded rural home. Deborah has recently been diagnosed, and the filmmakers hope to capture the raw, emotional toll the degenerative condition takes on a family. However, as filming progresses, Deborah’s behavior diverges sharply from standard medical expectations. Rather than typical forgetfulness, she experiences violent outbursts, exhibits profound psychological distress, and displays an encyclopedic knowledge of languages and historical trivia she never previously possessed. She wanders into the woods at night, whispers menacingly in the dark, and vandalizes her own home, carving cryptic symbols into her skin and walls.Sarah struggles to maintain composure, torn between caregiving duties and mounting terror as her mother deteriorates physically and mentally. Mia and her crew notice bizarre anomalies on their footage—glitches, eerie audio distortions, and split-second glimpses of a figure standing behind Deborah. Suspecting something far more sinister than neurological decline, the crew investigates Deborah’s past and uncovers a connection to a local pediatrician, Henry Desjardins, who mysteriously vanished decades prior. They learn that Desjardins was a practitioner of horrific occult rituals, kidnapping and sacrificing young girls.The investigation reveals the chilling truth: Deborah is not merely suffering from dementia, but is actively being possessed by the lingering,
malevolent spirit of Desjardins. The doctor intended to complete a macabre ritual requiring the sacrifice of a young girl to achieve immortality, but was interrupted. Now, decades later, he is attempting to finish the ceremony using Deborah as his vessel. The possession accelerates rapidly, turning Deborah into a terrifying, unnatural entity.The situation spirals out of control when Deborah kidnaps Cara, a young local girl afflicted with cancer, planning to use her as the final sacrificial victim. Sarah, Mia, and the crew track them down to a remote, abandoned hospital where the final ritual is underway. In a desperate, bloody rescue attempt, the crew confronts the possessed Deborah, who demonstrates superhuman strength and terrifying agility. Sarah fights desperately to reach her mother's consciousness, pleading with her to resist the entity. Just as the ritual nears completion and police arrive, Sarah manages to physically interrupt the ceremony, halting the sacrifice. Deborah seemingly returns to her senses for a fleeting, heartbreaking moment, recognizing her daughter before the chaos peaks. Although Cara is saved and taken to safety, the film concludes with a deeply unsettling realization: while Deborah was physically rescued, medical examinations in the aftermath reveal that the malevolent entity has successfully migrated from Deborah's broken body into the innocent, unsuspecting young girl, leaving the ultimate horror unresolved.