Investigator Enzo Vitello, a man and father with a dark past, investigates Dostoevsky, a killer who always leaves a letter with his vision of the world next to his victims.

Vitello secretly exchanges messages with the killer, while trying to deal with the drug problems of his daughter, Ambra, who he abandoned years earlier.

Vitello follows the clue in the last letter and explores the trail of former orphans. When the letters are released to the press Vitello is betrayed and his investigation compromised.

Vitello discovers who Dostoevsky is, a victim of the orphanage under a dark influence, and confesses to his daughter the reason for his departure years ago.

Vitello tracks down Esposito, Dostoevsky's weapons supplier, and forces him to ask the killer to join them, to arrive at the final face to face.