An adventure seeking couple, Eric and Jennifer convince their friends Yolanda and Viktor to explore an uncharted cave system in far North Australia, with the help of the unpredictable Cash as their guide.
The five spelunkers abseil into the deep mouth of the cave as a storm approaches, none are worried by the forecast, knowing they'll be safe underground. But when the caves are flooded, they become disoriented and tensions rise as they struggle to find a way out. But dark air and rising water are the least of their worries as they discover the storm has also brought in a hungry and territorial predator.