An accident during the construction of a tunnel beneath the Bering Strait leads to the discovery of a network of caverns and evidence that hints at the survival of a primitive human species. Led by DARPA technologist Reinhard Thyssen, a team of experts from around the globe is dispatched into the subterranean maze to discover all they can before the caves completely flood. Something lurks in the darkness, though . . . a creature that has evolved into a predator unlike any the world has ever known, and it's up to the scientists to make sure that it never reaches the surface. If they can survive that long.