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 paralysing 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,...