As civil war between Caesar and Pompey engulfs the Roman world, Gordianus the Finder receives an anonymous message informing him of the death of his son Meto who has been acting as a double agent for Caesar. The search for Meto's fate brings Gordianus to the besieged seaport of Massilia, which is stubbornly holding out against Caesar's troops. As famine and slaughter threaten the blockaded city, Gordianus is drawn into the intrigues of exiled Romans and duplicitous Massilians. His only friend in the city, Hieronymous, has been made the doomed scapegoat elected by city officials to bear the sins of the populace and save them all from annihilation. Meanwhile, Gordianus is constantly frustrated in his efforts to find out what happened to his son - and when he witnesses the fall of a young woman from a precipice outside the city called the Sacrifice Rock, then the plot begins to thicken...
