When a sink hole opens up near the Australian outback town of Pintalba, it uncovers a pristine cave system. Sam joins an expedition to explore the subterranean passages as paramedic support, hoping to remain unneeded at base camp. But, when one of the cavers is injured, he must overcome paralyzing claustrophobia to dive pitch-black waters and squeeze through the bowels of the earth. Soon he will find there are fates worse than being buried alive, for in the abandoned mines and caves beneath Pintalba, there are ravenous teeth in the dark. As a savage predator targets the group with hideous ferocity, Sam and his friends must fight for their lives if they are ever to see the sun again.