The place is Ostia, the port of Rome. Flavia Gemina, a Roman sea captain's daughter, is about to embark on a thrilling adventure.
When the dogs on Flavia's street start dying, she is determined to find out who is killing them and why. Her investigation leads her to three extraordinary people: Jonathan, her new neighbor; Nubia, an African slave girl; and Lupus, a mute beggar boy. They become firm friends as they search for the killer, narrowly escape being kidnapped by a slave dealer, and uncover a series of burglaries.