After a group of biologists discovers a huge network of unexplored caves in Romania and, believing it to be an undisturbed eco-system that has produced a new species, they hire the best American team of underwater cave explorers in the world. While exploring deeper into the underwater caves, a rockslide blocks their exit, and they soon discover a larger carnivorous creature has added them to its food chain.
When a frightening wave of violence sweeps through New York City, troubled cop Sarchie fails to find a rational explanation for the bizarre crimes. However, his eyes are opened to a frightening alternate reality when renegade Jesuit priest, Mendoza convinces him that demonic possession may be to blame for the gruesome murders. Together, they wage a valiant supernatural struggle to rid the city of an otherworldly evil.