Emperor Justinian's former Lord Chamberlain, John, gets a letter from his longtime comrade, Felix, and, placing loyalty to a friend above his own safety, risks defying imperial edict by leaving his exile in Greece for Rome where Felix is in some kind of trouble. For years a Captain of the Excubitors at the court in Constantinople, Felix has achieved his ambition to become a General when Justinian sends him to serve under General Diogenes in fighting for Rome against the besieging Goths. John's covert entrance into Rome is ambushed, driving him deep into ancient catacombs before he exits into the heart of the city. Arrested and brought before Diogenes, John learns that Felix is missing. It has been two days since he went to call upon Archdeacon Leon, a troublesome man at the heart of Felix's dispatch to the city. When sent to lodge at Felix's quarters, John finds the household in disarray, evidence that Felix has taken a questionable lover and run up his usual debts, and someone is rifling supplies. Then a young woman servant, also missing, is found dead. John has many mysteries to solve before Diogenes' courier to Justinian can return and prompt John's immediate execution.