The X Tuscolano is entrusted with an operation of the utmost importance: to take to the incinerator 50 kilos of pure drugs seized from Rambaldi, an internationally wanted drug trafficker. The Cerrone brothers, two fanatical criminals, are also interested in the load that they want to resell to Rambaldi himself and will do anything to steal it from the police officers. Meanwhile, Nina is in a new hideout. Berti and Marchetti investigate the murder of Sarah, an irreproachable thirty-year-old secretary of an important financial broker. Her mother Daniela, worried about the girl's silence, finds her body, hermetically sealed in the closet of her house. Commissioner Fontana takes care of the difficult case (the murderer seems to have left no trace), also committing himself to mending the relationship with Nina.