Following the funeral, Falco is astounded to discover that his father has left him and the rest of the Didii family a sizeable fortune.

He travels to the towns south of Rome with his adopted daughter Albia (who is unhappy that Falco's brother-in-law Aulus has married someone else) to look for Modestus but can't find him.

A clan of Imperial freedmen in the Pontine Marshes, the Claudii (consisting of four siblings named Nobilis, Probus, Virtus and Pius and their wives and female siblings) are implicated in Modestus' grisly murder but as Falco and Petronius investigate further, they attract the interest of the Imperial Chief Spy, Anacrites who, as usual, takes the case away from them.

The Didii, Camilli (Falco's in-laws) and Petronii families realise that they know too much and their lives (and possibly even the Flavian dynasty) are perhaps threatened by this missing brother.

Forced to make a difficult decision, Falco and Petronius take matters into their hands, conspiring to "send Nemesis to deal with him" once and for all.