Blood Vengeance is the first book of the Gaius Marius Mystery series, the memoire of Gaius Marius Insubrecus, the Urban Prefect of Roman Milan, and a retired Roman soldier, who fought with Caesar throughout his Gallic campaigns and the Roman civil war, and who supported Caesar's heir, Octavius, against Caesar's murderers and finally against Antonius and the Egyptian queen, Cleopatra.

Blood Vengeance recounts Gai's first year in charge of the vigiles, the watchmen who serve as the city police force and fire brigade. In the cold darkness of an early spring night, someone dumps the body of a retired Roman centurion at the feet of Augustus' newly intalled statue in the town forum. Whether an act of political violence by the disgruntled Gallic population of the town or a warning to Gai himself, who protects a secret so deadly it threatens him, his family, and his closest friends, Gai must uncover the murderer and insure his silence.