AD 454. Three years after the Roman victory over Attila the Hun at Catalaunum, Arria Felix and Garic the Frank are married and enjoying life on Garic's farm in northern Gaul (France). Their happy life is interrupted when a cryptic message arrives from Arria's father, the esteemed Senator Felix, calling them to Rome. At Arria's insistence, but against Garic's better judgment, they leave at once.

On their arrival at Villa Solis, they are confronted with a brutal murder and a dangerous mission. The fate of a profound and sacred object—Christ's Crown of Thorns—rests in their hands. They must carry the holy relic to the safety of Constantinople, away from a corrupt emperor and old enemies determined to steal it for their own gain. But a greater force arises against them—a secret cult who will commit any atrocity to capture the Crown. All the while, the gruesome murder and the conspiracy behind it haunt Arria's thoughts.

Arria and Garic's marital bonds are tested but forged as they partner together to fulfill one of history's most challenging missions, The Quest for the Crown of Thorns.