Bruno Testori is the director of the San Michele prison where he uses unorthodox methods towards the prisoners. One morning the body of Nicola Iaccarino, commander of the penitentiary police and best friend of Bruno, is found, who does not want to spread the news and begins internal personal investigations that will lead to nothing. Testori then turns to the deputy prosecutor Lombardo who investigates alongside Inspector Pellegrini discovering that the commander was attacked on the roof and thrown downstairs. Testori seeks the help of Miroslav Lackovic, a former drug trafficker serving a life sentence, to try to understand what really happened but he is found hanged in his cell.