The Roman Empire's conquest of Britannia is under threat from within. Prefect Cato and Centurion Macro must uncover a traitor to prevent unthinkable defeat. A messenger on the streets of Rome has been intercepted and tortured, revealing a plot to sabotage the Roman army's campaign against Caratacus, commander of Britannia's native tribes. A treacherous agent's mission is to open a second front of attack against them and eliminate the two Roman soldiers who could stand in the way.