The new commissioner Fontana introduces himself to the agents of the X° Tuscolano and the new inspector Marchetti. He must protect a collaborator of justice, Nina Neri. The police are looking for Jacopo, a three-year-old boy taken from his mother at the supermarket.

Young Angela is raped at night by three masked men, just outside a gay nightclub. Fontana entrusts the case to Luca Benvenuto. Angela has recognized by the voice a boy who frequents her gym and Luca infiltrates it.

Two drug addicts rob a bar where Inspector Marchetti is, and steal his gun. That day, a ministerial inspection is underway at the district and Marchetti risks suspension. Alessandro helps his friend recover the weapon.

Alessandro and Raffaele investigate the serious accident that happened to sixty-year-old Mario Fabiani: it seems that the car he was driving was hit by a boulder thrown from the overpass above. Meanwhile, Luca notices that his neighbor Nick, a child who has become fond of him and Anna and who always stays at their house, has clear signs of abuse on his body. Nick lives with his mother Emilia who is summoned for checks at the X° Tuscolano.

Irene is in Manila and Sacha's instrument shop for her nephew Stefano's guitar when a parcel bomb arrives that causes a tremendous explosion. Who could have it in for the two brothers and why? In the meantime, Nina has been tracked down by her father's right-hand man, Morace, due to Berti's carelessness. Morace is already in Rome and Fontana decides to interrogate Vanessa, Nina's friend and her only link with Calabria. In the meantime, DIA Major Saverio Patrizi arrives, whom PM Corradi has decided to place alongside the protection program of the X Tuscolano.

Massimo, a ten-year-old boy, follows a stranger in a white van. His anguished father Lucio reports his disappearance to the X Tuscolano. The investigation leads Anna to relive the trauma she suffered as a child with her stepfather and to make a serious error of judgment. Meanwhile, Commissioner Fontana, worried about Nina's escape, convinces his friend Vanessa to come to Rome to make an appointment with her and put her back under protection. Unfortunately, Morace is also in the city, determined not to let the girl testify against her father.

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: but her father has managed to talk to her and the girl no longer knows whether to trust her friend Fontana and collaborate with justice.

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: in fact, the girl has decided that she no longer wants to collaborate and is leaving with Major Patrizi for a secret location in Germany.

Lorenzo, director of a drug rehabilitation center, asks for the help of Agent Valli to discreetly solve a crime that took place in the center: a former heroin addict now a night watchman was found dead in the warehouse. Irene is worried because her sister Valeria, Stefano's mother who has not yet managed to detox, also lives in the farmhouse and she fears that she may be implicated in the affair. Under stress, Valli also faces Tiziana Cattaneo, the charming coroner responsible for her breakup with Alessandro.

A criminal gunsmith is found brutally murdered in the back room of his front shop. The agents of the 10th Tuscolano investigate and a neighbor recognizes Petrocchi from the signs, an elderly thief expert in safes, now on semi-liberty. The man denies being in the business but a nasty surprise awaits him. In the meantime, the statements of Nina, who has decided to collaborate without further reticence, cause many arrests in the clan and the escape of a fixer who asks for Fontana's protection.

Following the attack on Commissioner Fontana by the fugitive Morace, archivist Parmesan risks his life due to a heart attack. Agents Valli and Gori investigate the death of a Nigerian prostitute who was trying to get out of the business, while Raffaele and Luca, struggling with the theft of a special ink for printing banknotes, make an unpleasant discovery about Giorgio, Anna's new boyfriend.

Among the documents of the murdered fixer, Commissioner Fontana, thanks to Nina's collaboration, finds evidence of a horrendous crime that allows the arrest of Neri Giorgio. But at the moment of the arrest the boss feels ill and Benvenuto is forced to follow him in an ambulance. In the meantime Raffaele investigates the attempted suicide of Marinella and Maurizio, a couple saved by their fourteen-year-old son Silvio. Agent Marchetti suspects a story of usury, which he experienced firsthand, and risks a lot with unorthodox procedures in order to frame the person responsible.

Rosanna is raped in her own home by a masked man who seems to have left no traces: the young woman, shocked, only remembers that the attacker had a slight limp. Anna and Irene investigate the case which presents analogies with other unsolved rapes. Agent Guerra and Ingargiola are instead tasked with tracking down a prisoner who escaped, strange coincidence, on the same day that the theft of a precious piano is reported.

Anna and Irene are in a club where a drunk woman seems to need their help. The two officers accompany Gabriella home where they discover the lifeless body of fourteen-year-old Enrico, the autistic son of the woman, who is immediately arrested. Ingargiola and Vittoria are instead on the trail of a famous hypnotist who pushes his victims to hand over their savings. Fontana organizes Nina's transfer to the prison where her father is incarcerated: Neri has asked for an interview with the girl who immediately accepted.

A beautiful Albanian girl is kidnapped by a shady thug but manages to call the X Tuscolano asking for help. Ugo records her call which allows to trace the place of the phone call and her identity: her mother confirms that the voice is that of Elena, who has just arrived in Italy with the dream of becoming an actress. Commissioner Fontana consoles Nina for having escaped danger but a fax found in Morace's hideout with the route that the agents had established to reach the prison confirms the terrible hypothesis of a mole.

Prosecutor Corradi decides to entrust Nina's safety exclusively to Major Patrizi. But Commissioner Fontana suspects that the latter is conniving with the Neri clan to eliminate the young woman. These are the worst hours for Fontana who sees her young friend completely exposed. Irene and Anna are also in crisis because the case of a homeless man who died during the night seems to ambiguously involve the son of their colleague Vittoria, the high school student Francesco.

Nina is operated on after the terrible fall from the terrace of the building where she was hiding. Marcello, his wife Cristina, Matteo and all the agents of the X Tuscolano are close to the brave girl who dared to challenge her father and the clan he heads. In the meantime Corradi and the guard agent, Martino, are interrogated at the precinct by Benvenuto: the two claim that Nina, depressed by the long limitation of her freedom, attempted suicide.

The agents of the X Tuscolano deal with the attempted suicide of Milena, a ten-year-old Ukrainian girl temporarily fostered by an Italian couple who adore her. The judge, however, is adamant and orders that the little girl return to her hometown immediately, despite Milena's claims that they mistreat her in the orphanage. The story takes a dramatic turn as Fontana's lucidity is put to the test by a man who wants to force his partner to keep the child she is expecting, going so far as to commit a sensational act.

Alessandro Berti is the district manager after Fontana's departure. He coordinates the service of Anna and Irene, responsible for the transfer of a batch of ancient pottery of immense value. Raffaele, who has never given up his suspicions about Gori's boyfriend, informs Luca of the progress made in the investigations on Giorgio Potenza and on a new lead, without even suspecting that the story is about to take a very dangerous turn.

Anna throws herself into work to forget the disappointment she has just suffered: with Raffaele she investigates the disappearance of twenty-year-old Marika, reported by her friend Pamela. Berti asks Valli for help in the Neri affair: the boss has in fact obtained house arrest. Fontana is working through his grief where his story began, in Calabria: he visits the grave of his best agent, Dante Santagata, Nina's boyfriend who was killed by Neri. And he has a strange encounter, which perhaps will give him the strength to react.

Berti and Boni of the forensic team investigate the murder of a Senegalese man outside the nightclub where the immigrant worked as a waiter. Fontana returns from his trip to Calabria and immediately confronts Neri, awaiting the trial that, according to his lawyer Mantovani, will clear him of all charges. Marcello promises the boss that his friend Nina will have justice and immediately returns to duty at the X Tuscolano, welcomed with joy by all the officers. His first move is to interrogate Corradi: the commissioner has in fact discovered the blackmail that has silenced the former prosecutor.

Marchetti is forced to confront his painful past, as the investigation into the murder of the owner of an arcade leads Anna to suspect Massimo Sepe, son of the criminal killed by Raffaele years before and now an employee of the victim. In the meantime, Cristina, wife of Commissioner Fontana, discovers that Matteo, at school, has received an explicit threat to their safety from two strangers. Marcello has the family placed under guard and with Irene and Alessandro sets a trap for Morace.

While all the agents of the X Tuscolano are looking for Commissioner Fontana, who disappeared in Morace's van, Berti and Ia Valli are called by Tiziana. The coroner of the X Tuscolano has recognized the body of Veronica Todeschi, sister of her friend Franca and asks for their help on the difficult case. The girl, very beautiful, seems to have been thrown off the cliff overlooking the place where the body was found. But who could have had it in for a student with an apparently irreproachable life?

Valli and Berti try to gather as much evidence as possible against Neri before the final trial, almost a farce without Nina's testimony. Anna, Luca and Raffaele instead investigate the death of Don Michele Martinelli, stabbed in his own sacristy. The parish priest, highly esteemed by the community of believers, however seems to hide a terrible secret, perhaps the cause of his murder.

What happened to the drug shipment that Neri and Mantovani were expecting from South America? Finding it is the only hope for Commissioner Fontana, since, as feared, without Nina's testimony the Court of Assizes acquits the 'ndrangheta boss of all charges. Neri is free again and all the agents of the X Tuscolano are engaged in a race against time to find the drugs before they are refined and put on the market. Fontana accepts the challenge, putting the safety of his loved ones, his wife Cristina and his son Matteo, at risk.