When the deputy commander of Rome's Imperial Security Service is assassinated on the island of Rhodes, Cassius Corbulo swiftly finds himself embroiled in the investigation. Assisted once more by ex-gladiator bodyguard Indavara and servant Simo, his search for the truth is complicated by the involvement of the dead man's headstrong daughter, Annia.

Braving hostile seas, Cassius and his allies follow the assassin's trail south aboard a ship captained by a roguish Carthaginian smuggler and manned by his disparate, dangerous crew. Their journey leads them to the farthest reaches of the empire; to a ruined city where the rules of Roman civilization have long been abandoned, and a deadly battle of wits with a brutal, relentless foe.