A group of four friends, including Malik (Edward Furlong) and Gen (Cerina Vincent), embark on a weekend getaway to an abandoned prospecting settlement in California, which leads them into the tunnels that stretch towards the Mexican border. There, they become embroiled with two Mexican drug dealers and their teenage sidekick, who are being stalked by ghost-like creatures. As the survivors try to escape, they uncover dark secrets about the old man who is observing them from a distance, and ultimately discover his sinister connection to the tunnels' gruesome past.