Four paranormal investigator YouTubers—Riley Brennan, Laura Tucker, David Reynolds, and Peter Bailey—collectively known as the Paranormal Paranoids, vanish while probing a derelict prison in the ghost town of Shelby Oaks. When their bodies are later recovered, all except Riley are accounted for, and only one of their two cameras survives, containing the terrifying footage of a clearly terrified Riley.
Seventeen years pass, and Riley’s sister Mia steps into the spotlight for a documentary about the disappearance. Mia insists that Riley could still be alive, drawing on Riley’s childhood night terrors and the sense that something unseen watched over her. Mia’s world is unsettled not only by the unresolved case but also by her own troubled marriage to Robert, strained further by their struggle to conceive. The sudden arrival of a stranger at Mia’s door—who utters the chilling line, “she finally let me go” before taking his own life—shocks the household and sets off a chain of unsettling discoveries. The dying man’s body yields a mini-DV labeled “Shelby Oaks,” and Mia begrudgingly watches the footage that resurfaces the Paranoids investigating both the prison and an abandoned amusement park, where Laura, David, and Peter are slain by a masked assailant who also captures Riley before the clip ends. A damp night at Mia’s home reveals a dog with glowing eyes outside, a detail that gnaws at her as she digests the clues.
Seeking answers, Mia sits with the former prison warden, who identifies the killer as Wilson Miles. The warden’s account of a riot that broke out after Miles arrived, followed by a strange computer malfunction that opened every cell even as Miles stood still, deepens the mystery. Mia uncovers a book in Riley’s belongings filled with occult symbols and begins to explore the legends of parasitic incubus and hellhounds, and she grows increasingly convinced that Riley became the target of a dark ritual. Robert, overwhelmed by Mia’s obsession, leaves her side.
Driven by a need for truth, Mia returns to Shelby Oaks. She seeks out Miles’s former cell, hoping to glimpse the place that sealed Riley’s fate. From the cell’s window, she glimpses the ruins of the amusement park in the distance and is suddenly attacked by a hellhound. Fleeing to the amusement park, she discovers a dilapidated farmhouse where she meets an elderly resident, Norma. In Norma’s basement, Mia unearths proof that Norma is Miles’s mother, and that Miles had abducted Riley. Under Norma’s influence, a devoted follower of the incubus Tarion, Miles relentlessly raped Riley in a perverse bid to conceive a child that would bear Tarion’s lineage. After a string of miscarriages, Riley finally gives birth to a healthy baby boy.
Mia keys her phone and calls for police as Norma guides her deeper into the house. Norma leads her to the basement, where Riley is imprisoned. Mia frees her, but Riley, consumed by fear and a claimed possession, grabs a fire poker and ascends to the main level. Mia witnesses Norma incapacitate Riley and perform a blood ritual over the newborn, with Tarion briefly appearing in the shadows. Norma dies from blood loss, and Mia greets the infant as police arrive.
Riley and the baby are transported to the hospital and discharged. That night, Riley, convinced the baby is possessed, attempts to smother it. Mia intervenes, and in the ensuing struggle, a desperate Mia ends up pushing Riley out a window. Riley survives the fall but is soon surrounded by hellhounds and is devoured. In the collapse of the case, Mia realizes that Riley’s childhood fear of being watched was Tarion’s way of watching both sisters—one to bear his child, the other to raise it. Tarion's presence returns, looming behind Mia as her eyes briefly glow, and she screams, signaling a chilling, unending cycle of possession and predation.
