Daniel Knox is a maverick Egyptologist and archaelogical dive expert. He's out of favour with most of the authorities and is earning a crust providing diving lessons to guests of shipping tycoon Hassan al-Assyuti. Until, that is, an argument with his brutal host puts his very life in danger. Hiding out from al-Assyuti's heavies with an archaeologist friend, Knox finds himself part of a team that stumbles across a catacomb in Alexandria. Inside the catacomb is a cipher that provides explosive information - clues to the location of Alexander the Great's tomb.