A year after a tragic car accident claims the lives of her husband and daughter, Sarah seeks solace and distraction by joining her friends on a caving expedition in the remote Appalachian Mountains. The group descends into what they believe is a well-mapped cave system—only to discover too late that it’s uncharted and treacherous. When a tunnel collapses behind them, cutting off their exit, the group must navigate the darkness in search of another way out. But deep within the cave, they uncover signs of previous, ill-fated explorers—and something far more terrifying. Lurking in the shadows are the “crawlers,” pale, blind, and feral creatures that hunt by sound, turning the underground adventure into a desperate fight for survival.