THE SAURIAN WAR RAGES ON Unaware of the brutal battle that has just taken place between Ursula, the giant Megalodon shark, and the macropliosaur designated Typhon, Dr. Derek "Dirk" Braddock seizes upon his mentor Eric Grayson's absence and launches a dual-pronged mission into Earth's bloodstained seas. His brother Garm, commanding the anti-biologic submarine Gryphon, is assigned the dubious task of hunting down and exterminating Typhon. Meanwhile, Natalya Dragunova, captain of the Antrodemus, prepares to penetrate the perilous waters of Diablo Caldera - the Cretaceous-era lake from which the savage pliosaurs originated. Neither of them has any idea what is waiting for them. Soon, Dirk's investigation into his mother's untimely death uncovers a shocking truth: one that, when revealed, will shake the research facility known as Tartarus, and his world, to the core. Malevolent forces are at work that Dirk is unaware of, and he soon finds himself fighting not only for his life, but the lives of everyone he loves. Meanwhile, lurking in the darkness of Tartarus's abyssal depths, the ultimate horror awaits . . .