Venturing into a vast subterranean nightmare populated with the most hideous creatures imaginable, mankind's last hope against a fiendish-and seemingly intelligent-disease is shattered! Beset by murderous, insanity-inducing beasts from all sides, the American scientific and military task force has become separated in a twisted underground realm. As their bodies begin to change in demoniac fashion, they must fight to keep their sanity... and avoid turning against one another.