Following Giulia Corsi's transfer, her deputy Roberto Ardenzi becomes the new commissioner of the X Tuscolano. During the inauguration ceremony, a gang of ferocious robbers breaks into the villa of a rich notary, easily deactivating the alarm system. One of the criminals shoots the professional's twenty-year-old son in cold blood, killing him. The cruel action sparks the rebellion of the only foreigner in the group, the Romanian Artur, who is killed after he announces his intention to leave the gang. During the investigation, Mauro will meet an old classmate, Alessandro Berti, who now works with the Scientific Police, while the new inspector Irene Valli arrives at the X Tuscolano one day late.