The sixth season begins with a change in the precinct leadership: Giulia Corsi moves to Trieste to follow Carabinieri Captain Rea, and her place is taken by Roberto Ardenzi, who is also in his final year at the precinct. Inspector Irene Valli and Inspector Alessandro Berti join the team.
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. Following an action conducted with the new commissioner Roberto, Mauro is taken hostage by the two brothers from Puglia led by the Neapolitan Gabriele, responsible for bloody robberies. Alessandro Berti of the Scientific Police offers himself as bait, allowing Roberto to hide and be taken to the hideout where his friend is about to be executed. After a terrible firefight, Mauro is freed by his colleagues.
The intuition of the new commissioner of the X Tuscolano Roberto is not wrong: behind the apparently casual death of the model Eva Paulin there is something more. The young woman, with the complicity of her brother Milo, stole precious objects from her rich clients. Milo has the commissioner receive a notebook that Eva had kept, before dying before his eyes. Francesca, found by her husband Roberto in a pool of blood in their home, must undergo emergency surgery. Both she and the baby are at risk of losing their lives. While Luca, Anna and Irene, investigating a strange accident with a dead person, discover that it is a rape with robbery involving one of their colleagues, Francesca regains consciousness and tells her husband about the attack she suffered at home.
The newborn Francesco, son of Roberto and Francesca, is saved after a long operation. He is immediately celebrated by his siblings Michele and Mauretta and by the agents of the X Tuscolano. The new commissioner understands that he must deal with a character from the past, Cesare Carrano, today an important builder and instigator of the attacker of Francesca by Maiorca. He is also the father of Ruggero, the murderer of Milo that Roberto wounded before the escape, now a fugitive. The new inspector of the X Tuscolano Irene Valli finds herself involved in a robbery in the store, where she and her nephew Stefano, eleven years old, happen to be. The two criminals do not hesitate to kill the owner of the store and beat the boy. With the excuse of wanting to treat him, Irene manages to make Stefano escape, who immediately calls Mauro. When the officers arrive, one of the criminals flees, taking a customer hostage.
The 10th Tuscolano is dealing with a thorny affair involving a rising politician: his blue car has hit and killed an immigrant. Roberto does not give up and tenaciously sets out on the trail of the killer Ruggero, son of the building contractor Cesare Carrano. Mauro asks his friend Ardenzi for explanations about a secret that he has kept from him until now while, with Irene, he tries to prevent the fugitive from escaping. Ruggero Carrano is in prison and the prosecutor Forti authorizes the interrogation by the commissioner of the 10th Tuscolano. But the father of the murderer and his right-hand man are preparing a plan for a spectacular escape, while Mauro and Irene investigate the case of a sixteen-year-old who died of an overdose; the surprise is that the boy turns out to be the son of a friend of Mauro, whom he protected years before.
The 10th Tuscolano is in turmoil over what happened during Ruggero Carrano's spectacular escape. Everyone questions their own life: Luca goes to visit his dying father; Parmesan reacts to his hypochondria; Vittoria and Ingargiola get closer again. Roberto confronts Cesare Carrano, but there to protect him from himself is the faithful Alessandro Berti. Carrano's right-hand man kills the members of the commando that allowed Ruggero's escape and now demands more money. The leader of the group manages to save himself: when Luca and Alessandro arrive at the crime scene, the head of the forensic team understands that the massacre is linked to the criminal organization headed by the Carranos. Thus begins a hunt for the survivor coordinated by Roberto.
While Irene and Anna investigate a villa robbery that ended in tragedy, Roberto asks Alessandro to remain on the force at the X° Tuscolano. With his help and the collaboration of Parmesan and Luca, the commissioner tries to decipher the code of the notebook written by Ruggero Carrano, finally in prison after Gabrielli's arrest. Alessandro Berti accepts the proposal of the commissioner of the 10th Tuscolano to work in tandem with Irene on the case of a murder that hides a trafficking of newborns. Roberto must deal with the legal expedients of the lawyer who defends Carrano: the request for a calligraphic expertise on the notebook that contains the details of the complex criminal organization managed by the entrepreneur, turns out to be a dangerous trap.
The 10th Tuscolano is busy hunting down two girls in their twenties who, in the space of a few hours, uncovered, burgled a boutique and stole a spider. The two seem intent on having a memorable day, but the youngest is eight months pregnant. Meanwhile, Roberto tries to corner Maiorca who has destroyed the coded notebook, the main evidence in the trial against the Carranos. On the eve of the trial against Ruggero Carrano, in which Roberto should participate as the main witness for the murder of Milo Paulin, Carrano's machinations do everything to discredit the new commissioner. This is how Ardenzi ends up being investigated by the disciplinary team for the murder of one of their operatives, whom he threatened several times after the destruction of the coded notebook.
A young Lithuanian, Jelena, turns to the X Tuscolano. The girl, in shock, has just arrived in Italy with a friend and her sister, all three convinced of entering the world of entertainment. She managed to escape but the other two remained, drugged, in the hands of an Albanian couple who intend to force them into prostitution. The agents know they have little time, while Roberto helps Tiberio, Mauro's father, to face a big problem. Cesare Carrano is studying a plan to get his son Ruggero out of prison, sentenced to twenty years for the murder of Milo Paulin. Parmesan receives from Roberto the task of demonstrating the responsibility of the entrepreneur, head of a large drug trafficking ring. Irene and Alessandro investigate the murder of a young courier in love with a married colleague.
While the criminal entrepreneur Carrano organizes his revenge, supported by Patriarca and his lawyer, the X° Tuscolano is mobilized for the kidnapping of the son of a very rich cement manufacturer. The kidnapper acts with original methods and does not seem so interested in the ransom he has asked for the same day. Vittoria and Ingargiola are instead dealing with a champagne thief. After the latest developments in the Carrano case, Roberto decides to take a break to spend some time with his family. He leaves the district in the hands of Alessandro Berti who, with Anna and Irene, tackles the investigation into a badly cut batch of heroin. There are already two drug addicts on the brink of death. During the investigation, Valli loses her professional detachment and brings her personal history into the case.
Investigating an arson attack, Alessandro and Irene meet a colleague from the explosives department who suspects a young but repeat offender. Simonelli takes it personally because he saw his best friend die during a fire set years earlier by the same deranged man. But Irene realizes that things are less straightforward than they seem, while Roberto manages to arrest the perpetrator of the car bomb commissioned by Patriarca. During a graduation party, a young and beautiful university professor is drugged and raped. But when she wakes up, Viviana doesn't remember anything and Luca and Anna will have to find out who took advantage of her. Meanwhile, Roberto, who has discovered Patriarca's home and hidden documents inside that concern a nursery, gets back on the trail of Cesare Carrano.
Cesare Carrano is declared a fugitive, along with his accomplice Patriarca. The entrepreneur's villa is seized and Parmesan and his nephew Christian are tasked with archiving all the objects. Meanwhile, Anna and Luca investigate the alleged accident that caused a Russian immigrant to fall from the fifth floor, discovering a universe of marginalization and degradation. Irene collaborates with Anna and Luca in the investigations into the disappearance of fourteen-year-old Daniela. The case will bring back Anna's painful past. The confession of an accomplice of Patriarca, who was arrested, forces Roberto to track down Francesca: in fact, the boss has very dangerous intentions towards them.
After the attack on the children, Francesca accepts the escort. Roberto discovers that Carrano has managed to track down his wife through a detective agency contacted by an unsuspecting mediator. Irene and Alessandro deal with the murder of an actor, an alcoholic now adrift, found murdered in his own boat. His ex-wife will help them solve the case. Roberto and Alessandro monitor the movements of the lawyer Grimaldi, the legal defender of Carrano, still at large with Patriarca. The other agents of the X Tuscolano are busy with the almost fatal attack on the young brother of a famous boxer. The investigations bring to light the boy's passion for clandestine betting and suggest the involvement of Nino who the night before almost lost an important match.
There will be the long-awaited showdown between Commissioner Ardenzi and Carrano, the one who is responsible for the death of Ardenzi's close friend, Inspector Mauro Belli. Until the very end, the challenge between Ardenzi and Carrano, long-time enemies, reserves sensational twists. And it turns out that not everything is as it seemed.
On the eve of the trial against Ruggero Carrano, in which Roberto should participate as the main witness for the murder of Milo Paulin, Carrano's machinations do everything to discredit the new commissioner. This is how Ardenzi ends up being investigated by the disciplinary team for the murder of one of their operatives, whom he threatened several times after the destruction of the coded notebook.
A young Lithuanian, Jelena, turns to the X Tuscolano. The girl, in shock, has just arrived in Italy with a friend and her sister, all three convinced of entering the world of entertainment. She managed to escape but the other two remained, drugged, in the hands of an Albanian couple who intend to force them into prostitution. The agents know they have little time, while Roberto helps Tiberio, Mauro's father, to face a big problem.
Cesare Carrano is studying a plan to get his son Ruggero out of prison, sentenced to twenty years for the murder of Milo Paulin. Parmesan receives from Roberto the task of demonstrating the responsibility of the entrepreneur, head of a large drug trafficking ring. Irene and Alessandro investigate the murder of a young courier in love with a married colleague.
While the criminal entrepreneur Carrano organizes his revenge, supported by Patriarca and his lawyer, the X° Tuscolano is mobilized for the kidnapping of the son of a very rich cement manufacturer. The kidnapper acts with original methods and does not seem so interested in the ransom he has asked for the same day. Vittoria and Ingargiola are instead dealing with a champagne thief.
After the latest developments in the Carrano case, Roberto decides to take a break to spend some time with his family. He leaves the district in the hands of Alessandro Berti who, with Anna and Irene, tackles the investigation into a badly cut batch of heroin. There are already two drug addicts on the brink of death. During the investigation, Valli loses her professional detachment and brings her personal history into the case.
Investigating an arson attack, Alessandro and Irene meet a colleague from the explosives department who suspects a young but repeat offender. Simonelli takes it personally because he saw his best friend die during a fire set years earlier by the same deranged man. But Irene realizes that things are less straightforward than they seem, while Roberto manages to arrest the perpetrator of the car bomb commissioned by Patriarca.
During a graduation party, a young and beautiful university professor is drugged and raped. But when she wakes up, Viviana doesn't remember anything and Luca and Anna will have to find out who took advantage of her. Meanwhile, Roberto, who has discovered Patriarca's home and hidden documents inside that concern a nursery, gets back on the trail of Cesare Carrano.
Cesare Carrano is declared a fugitive, along with his accomplice Patriarca. The entrepreneur's villa is seized and Parmesan and his nephew Christian are tasked with archiving all the objects. Meanwhile, Anna and Luca investigate the alleged accident that caused a Russian immigrant to fall from the fifth floor, discovering a universe of marginalization and degradation.
Irene collaborates with Anna and Luca in the investigations into the disappearance of fourteen-year-old Daniela. The case will bring back Anna's painful past. The confession of an accomplice of Patriarca, who was arrested, forces Roberto to track down Francesca: in fact, the boss has very dangerous intentions towards them.
After the attack on the children, Francesca accepts the escort. Roberto discovers that Carrano has managed to track down his wife through a detective agency contacted by an unsuspecting mediator. Irene and Alessandro deal with the murder of an actor, an alcoholic now adrift, found murdered in his own boat. His ex-wife will help them solve the case.
Roberto and Alessandro monitor the movements of the lawyer Grimaldi, the legal defender of Carrano, still at large with Patriarca. The other agents of the X Tuscolano are busy with the almost fatal attack on the young brother of a famous boxer. The investigations bring to light the boy's passion for clandestine betting and suggest the involvement of Nino who the night before almost lost an important match.
There will be the long-awaited showdown between Commissioner Ardenzi and Carrano, the one who is responsible for the death of Ardenzi's close friend, Inspector Mauro Belli.
Until the very end, the challenge between Ardenzi and Carrano, long-time enemies, reserves sensational twists. And it turns out that not everything is as it seemed.