Meet Maddox Holloway, a 9-year-old boy in rural England, 1940. With his father at the front lines of World War II, a dark affliction slowly consumes his mother, twisting her into something monstrous. Mutter follows Maddox’s harrowing struggle as he faces fear, suffering, and a crushing sense of responsibility, confronting the creature his mother is becoming while holding onto who she once was.