Marcus Salvius Magnus solves the rivalry between a brothel owner under his protection and a rival protected by a gang from a neighbouring area in Rome in such a way as to also do a favour for Antonia, sister-in-law of the Emperor Tiberius.
This story of mafia style gangs in the lower reaches of Roman society paints a rather harsher picture than I'm used to, but the story grabbed my attention and was quite impossible to put down.