In need of money to pay both his landlord and an angry bookmaker, Falco--a private detective living in Rome, circa 69 A.D.--is asked to find the missing brother of Helena, the daughter of a prominent senator and wife to Pertinax, the head of the emperor's guards. Having been given title to a sensitive gladiator named Justus in exchange for an overdue bill, Falco finds the young boy's body in the catacombs as it is about to be buried. After returning to his gladiator's school where Justus falls for the female gladiator Druida, Falco suspects a failed attempt on his own life is connected with the inquiry into Cato's death. Then, while at the boy's funeral, Falco spots the head of a fertility cult joined by Cato and, arriving at the Temple of Cybele to question Priestess Saleena, is also surprised to find his own nephew Curio. Though the artisan suspected of making the knife used to kill Cato nervously denies any knowledge of the weapon, Falco soon learns it belongs to the Emperor's son, Domitian. Then, after Falco is imprisoned by the emperor's guards and Helena inquires as to his whereabouts, Justus first dispenses some timely advice to Druida before helping his master to escape. As Falco goes in search of Cato's killer at a masked ball hosted by Saleena, Justus returns to see Druida, but is forced to flee as she is readied to fight again -- this time for Emperor Vespasian himself. When Helena and her father are arrested as part of the coup against the emperor, Falco is also imprisoned and taken to the palace. Then, at a royal banquet where Domitian surprises his father with a battle between Druida and Justus, traitorous guards seize Vespasian in a plot to overthrow him. But, after summoning loyalist troops to the rescue, Falco explains how Saleena and Pertinax plotted to kill Vespasian and blame Domitian. Finally, released from slavery and made a free man, Justus sets out on his own after a final visit With Druida, while Falco succumbs to the seductions of a grateful Lady Helena.
