In the frozen tundra of Greenland, a group of modern-day researchers stumble on a shocking find: a medieval ship buried a half-mile below the ice. Inside the captain’s cabin is a clockwork gold map embedded with an intricate silver astrolabe. Once activated, the moving map traces the path of Odysseus’ famous ship as it sailed away from Troy. But the route detours as the map opens to reveal a fiery river leading to a hidden realm underneath the Mediterranean Sea. It is the subterranean world of Tartarus, the Greek name for Hell. The phantasmagoric horrors found in Homer’s tales are all too real --- and could be unleashed upon the world. Now, Sigma Force must go where humans fear to tread. To prevent a tyrant from igniting a global war, they must cross the very gates of Hell.