Marshal Rocca goes to Rome to attend the funeral of a cobbler friend and here he meets Benedetto with his wife Elisa, his old flame. Back in Viterbo, he begins to investigate the murder of a gas station attendant's son, which appears to be connected to two robberies. Meanwhile Rocca receives a visit from Elisa, who disappears after revealing that she is in crisis with her husband; Benedetto also arrives in Viterbo in search of his wife, whose car is found in a ditch. A woman friend of Elisa's is then found dead, who could be connected to the robbery and who also turns out to be the sister of a man arrested years earlier by Rocca because he was found guilty of killing a music teacher, loan shark and paedophile; he too is found dead in a farmhouse from the wounds sustained in one of the two robberies. Meanwhile Benedetto attempts suicide after the discovery of Elisa's body: the marshal will save him.

Benedetto confesses to Rocca that it was Elisa, the object of harassment, who killed the music teacher and that he had helped her to frame a man in her place. Once the sentence had been served, the latter had been hosted by the two spouses, oppressed by guilt; Elisa becomes his lover and accomplice in the robberies. Meanwhile, the marshal learns from his son Giacomo that the blood found near the cobbler's body belongs to Elisa's lover, who took refuge in his shop after a robbery: it is in this room that part of the booty will be found and it is by reconnecting the things that Rocca he will induce Benedetto to confess to the murder of his wife, her friend and the cobbler, all guilty of wanting to steal his share of his money. The assassin seems to want to follow Rocca to the barracks, but he commits suicide by jumping into the void. With Tommy and Francesca, the legendary marshal will continue his life in Viterbo.