Centurion Aurelius Castus has been summoned back from Britain, to find himself caught in a conspiracy threatening to bring down the Emperor Constantine. Rewarded for saving the emperor's life in battle, Castus is promoted to Corps of Protectores, the elite imperial bodyguard—the swords around the throne. But he soon discovers the court is as dangerous as the battlefield; behind the gilded facade of empire, there are plots, betrayals and seductions, a nest of traitors, and one relentless enemy.