Spanning Europe and Africa, Josh's chase for Alexander's remains and fortune ramps up. Clues mount in a flooded ruin beneath Alexandria, Egypt. Later, Josh gathers shocking evidence Alexander's body may actually lie in Venice's St. Mark's Cathedral.

Just off Florida's coast, Josh Gates braves shark-infested waters in search of an American ship sunk by a Nazi U-boat during WWII. Josh joins Tristan Guttridge who has a bold new strategy to use sharks as spies to uncover the wreck.