Frank and Joe have come to Germany to assist archaeologist Dr. John Maxwell in his search for a legendary jewel-encrusted shield. The priceless artifact is rumored to be buried in the lost ruins of an ancient Roman fortress. But the boys discover more than the shield is missing: Maxwell himself has vanished without a trace!

Hunting for both Maxwell and the shield, the Hardys make some powerful, ruthless enemies. From vicious attack dogs to armor-clad thugs, they face a new fight at every turn. But as they descend into a labyrinth of lies, Frank and Joe are determined to unearth the truth ... no matter how deep, dark, and dealy it is!