A group of anthropologists uncover strange inscriptions on the wall of a Colorado mine just as an explosion traps them deep within the earth. But their work won't stay buried long. Dirk Pitt is on hand during the blast and quick to initiate a rescue operation. He is then tapped to lead a research crew on behalf of the U.S. National Underwater and Marine Agency to further study these uncanny artifacts. And that's when his ship is set upon and nearly sunk by an impossibility—a vessel that should have died 56 years before. Clearly, another group knows about the relics of this long-forgotten but highly-advanced seafaring culture. And they'll stop at nothing to keep the rest of the world in the dark.