Fleeing the massacre of his entire family save a single uncle, young Roman aristocrat Quintus Varrus arrives in fourth-century London not knowing who is to blame for the murders nor whom he can trust now. He fears for his life, but when he meets a young Irish woman named Lydia Mcuil, their lives quickly become intertwined and her father offers to set the young Roman up as a smith (under an Irish alias) in the town of Colchester while the young lovers get to know each other from a distance. But the assassins haven't forgotten Quintus and a deadly ambush is barely thwarted, bringing the young Roman into friendship with his rescuer, a hardened former military policeman known as Rufus Cato, who has his own score to settle with the powerful man behind the attack. Quintus is introduced to the secrets of a powerful, ancient brotherhood that is trying to halt the rot that is destroying their beloved Empire--secrets that may finally reveal the identity of those who murdered his family, and expose the shocking reason why.