Jack McAllister one of two thrill-seeking professional cave explorers, along with his brother Tyler. His team of expert cave divers, led by him, is hired to explore a vast, unexplored cave system discovered beneath a 13th-century Romanian abbey. The team includes Jack's brother Tyler, Top Buchanan, Dr. Kathryn Jennings, Charlie, Briggs, and Alex Kim. The team of cave divers who become trapped in a newly discovered cave system in Romania and encounter deadly, mutated creatures. Jack sacrifices himself by causing a cave-in, allowing the others to escape.