Martin Bristol, a young boy with congenital analgesia, is kidnapped by the psychotic and grieving serial killer Graham Sutter, Brett Rickaby. In an abandoned slaughterhouse once run by his family, the killer slashes Martin’s cheek and executes a captive young woman right before him. Martin attempts to escape, but Graham recaptures him and returns him to the slaughterhouse, where the boy is kept with future female victims, forced to witness each brutal act.
Over the next five years, Graham brutalizes several young women, forcing Martin to watch as the trauma slowly desensitizes him. Graham, who feels guilt over killing the cattle he once cared for, talks to the skull of a bull hung on the wall, treating it as a mighty deity. It’s implied that he was abused by his father and eventually murdered him, concealing the corpse under a sheet in the attic.
After the deaths of her parents, Allison Miller, Alexandra Daddario comes to live in Minersville with her paternal uncle Jonathan Miller, Michael Biehn, her aunt Karen, Kathryn Meisle, and her cousin Wendy. While out for a run, she spots Martin Spencer List through the window of the supposedly abandoned slaughterhouse beside Graham’s farmhouse, and later meets a local boy named William, Nolan Gerard Funk.
One night, Jonathan intervenes as Allison and William are about to have sex. The next day, Allison returns to the farmhouse after again seeing Martin in the slaughterhouse window and is captured by Graham. When she doesn’t return home, Jonathan drives to the farmhouse to look for her, but Graham shoots him dead. William, also searching for Allison, finds Jonathan’s abandoned car and discovers Allison locked inside a cold meat room; he tries to rescue her but Graham kills him.
Graham has grown fearful of Martin’s inability to feel pain and pins Martin’s hand to the kitchen table with a knife to keep him from leaving. Allison escapes by pushing a metal rod through a hole in the door and lifting the lock, freeing Martin as well. She finds Martin with his hand still pinned and carries him out of the farmhouse.
Graham takes Jonathan’s body to his home and attacks Karen, who tells Wendy to run. Wendy runs upstairs and hides in her closet, listening as her mother dies. Allison arrives just as Graham sets the house on fire. Graham finds Wendy and intends to use her to replace Martin as his assistant, but Allison interrupts and stabs Graham, causing him to flee. Martin then stabs Allison to death, his mind now completely warped by years of abuse. He kills Wendy before leaving the burning house.
The authorities arrive at the smoldering ruins of the Miller home the next morning and rule it an accident. Martin begins constructing a new skeletal shrine inside the farmhouse, with the bull’s skull as its head, and he stares out the window, waiting for his next victim.
In a post-credits scene set five years later, Courtney Harrison, Courtney Bertolone (archive footage / uncredited), flees from an unseen pursuer, enters the farmhouse, and discovers Martin, now older, Jay Cohen sitting at a table. When she asks for help, Martin slowly turns toward her, and the film ends.
