At the Vatican, a mysterious package arrives for the head of Pontifical ancient studies, sent by a colleague who vanished a decade earlier. It contains two strange artifacts: a skull scrawled with ancient Aramaic and a tome bound in human skin. DNA testing reveals both are from Genghis Khan—the long-dead Mongol king whose undiscovered tomb is rumored to hold the vast treasures and knowledge of a lost ancient empire.

Commander Gray Pierce and Sigma—joined by a pair of Vatican historians—race to uncover a truth tied to the fall of the Roman Empire, to a mystery bound in the roots of Christianity's origins, and to a weapon hidden for centuries that holds the fate of humanity.