After a car accident leaves her unconscious, a young woman named Michelle ( Mary Elizabeth Winstead ) awakens to find herself trapped in an underground bunker. Her captor, a doomsday prepper named Howard ( John Goodman ), insists that a catastrophic attack has rendered the outside world uninhabitable, forcing her to rely on his volatile hospitality. Alongside a fellow survivor, Emmett ( John Gallagher Jr. ), Michelle must navigate the claustrophobic tension of their new reality, questioning whether the threat on the surface is real or a paranoid delusion. Director Dan Trachtenberg masterfully crafts a taut psychological thriller that blends sci-fi unease with palpable human dread, keeping audiences guessing at every turn. As Michelle’s desperation to escape grows, she must decide if the truth beyond the bunker’s walls is worth the risk, even if it means facing an unknown horror.