Before the Mobile can stop him, Leo manages to talk to Pulcino and trace the name of the person who stole Luca's cell phone. The investigation focuses on the world of prostitution and leads again to the name of Ekaterina Ratnikova. Only that the girl, at this point, has disappeared. After the search of Ekaterina's house, the men of the X Tuscolano discover that the relationship between Guarinelli and his informant is much more than a simple professional bond. Now all they have to do is tail the policeman and wait for him to give himself away, but the task turns out to be more difficult than expected.