Gaius Valerius 'Floppy' Flaccus is the friend and later love-interest of Flavia Gemina.
Flaccus first meets the girl detective Flavia in The Colossus of Rhodes when she is sailing to Rhodes on her father's ship. At first she does not like him, saying that he is a "pompous lawyer", and nicknaming him "Floppy". He is also arrogant and rude to her but by the end of the book she is sad to see him leave, as she has seen his true character as a noble, kind, just man. He is also incredibly handsome.
In The Sirens of Surrentum, he meets Flavia again, but he leaves not long after with a mission to help Flavia track down a criminal mastermind. Nubia starts to suspect that Flaccus may be falling for Flavia and hints at this.
He appears again in The Slave-Girl from Jerusalem, defending Hephzibah bat David in court, and Flavia starts to fall for him. He proposes to her at the beginning of The Beggar of Volubilis, only to be turned down, as Flavia has taken a vow of chastity at the temple of Diana. He leaves her with a betrothal ring, in case she changes her mind, and the feathered end of an arrow, as a symbol that she has pierced his heart. Unbeknownst to him, at the end of The Beggar of Volubilis, Flavia is tempted to change her mind regarding his proposal.
In the Prophet of Ephesus Flavia meets him in Halicarnassus where she finds out he is betrothed to Prudentilla. Flavia realises that she really loves Flaccus and wants him to marry her.
At the end of The Man from Pomegranate Street, Flaccus pretends to have drowned in a shipwreck, in order to leave his life in Rome behind to follow Flavia to Ephesus. He uses the name 'Jason' as a cover name. He and Flavia marry at the end of 'The Man from Pomegranate Street'.