Expert cave diver Curt Bowen and his team of intrepid explorers are on a deadly quest to explore and find the answers to history's buried secrets that are submerged in underwater caves across the globe. But finding the answers could cost them their lives. The truth they seek is deep underground in a haunting, alien landscape few humans ever have seen. Traveling to the farthest corners of the globe and following a trail of evidence
that leads them ever deeper into the silent, deadly world that lies below, Curt and his team risk it all beneath the Earth's surface. The beauty they encounter is matched only by the danger they must face as they journey into the "Underworld."