The film unfolds in two distinct acts. The first act follows Lucie, a young woman who escapes a mysterious industrial slaughterhouse where she was tortured for years. She hunts down the seemingly normal family she believes is responsible, aided by her friend Anna. The second act pivots radically: Anna discovers a hidden basement containing a woman who has been flayed and kept alive for years. She learns that a secret society is torturing victims to induce a state of "martyrdom"—a transcendental vision of the afterlife. The final line, "Keep doubting," has sparked film theory debates for over a decade.