One Saturday afternoon in September 1955 a young Italian attorney, Sal Dematteo, while visiting the Carnegie Museum in Pittsburgh, views an elaborate dagger and begins having visions of ancient Rome and Judea. As these episodes increase, interrupting his life, he consults his Jewish law partner, David Gold, and the two embark on a journey to find the meaning of Sal's episodes and make them stop.

It appears the visions have a relationship to history and are connected to Flavius Josephus, a historian and descendent of an old Jewish family. Josephus was a top military commander in the Jewish Army in the Galilee and allegedly defected to the Romans after the siege of the fortress city of Jotapata.

As the quest evolves, others become deeply involved, including a psychiatrist, his nurse, a priest and a rabbi. An archaeologist, who calls himself a time detective, is also called in to help them in their search. They learn the dagger, which belonged to the ancient lawgiver, Hammurabi, was passed down through generations of Babylonian Emperors, and is now being sought by the Sicarians, a secret band of assassins who threaten the lives of those involved.