A quiet Sunday in Rome... for the police officers of the Flying Squad, however, Sundays, like the rest of the days, are never quiet. This Sunday in particular, everything happens. It would be Ardenzi's birthday but between stalking, drug trafficking and women who want to throw themselves into the Tiber, the day seems to never end. / The Flying Squad is dealing with a typical day at work in the Capital. An old friend of Ardenzi, a well-known restaurateur in the historic center, turns to the commissioner to solve a problem with his son. Meanwhile, a young girl who is not yet of age is taken to the police station together with the man who lured her.

Zaccardo, head of the Section, informs Ardenzi and Sabatini of an upcoming very important operation to capture a fugitive in a Roma camp in the Capital. They must prepare and carry it out as best they can. This obviously while emergencies arrive at the Police Headquarters. / Today is the day of the blitz. The team is finalizing the final preparations but the police headquarters receives a report of a woman run over on Lungo Tevere, and moreover the daughter of a repentant.

While at the police station Claudio Sabatini is looking for a way to free Bradic, who is being held awaiting questioning, without arousing the suspicions of his colleagues, Ardenzi and Sandro are dealing with the case of a Pakistani girl stoned to death in the street and Isabella is dealing with her first serious friction with her boyfriend Giulio who ends up slapping her with serious consequences. / Bradic's death at the police station and at the hands of Marcello, forces the commissioner to put the young policeman under investigation and for this reason Oliviero, feeling misunderstood and unjustly accused, runs away and disappears. Ardenzi is worried about the boy, he wants to find him and it is his job to clarify the dynamics of the facts; Claudio Sabatini also needs to find Marcello.

The death of Marcello has shocked the entire team but the worst blow was suffered by Roberto who feels responsible for the boy's disappearance and is now determined to understand what happened. In the meantime, Sandro and Giacomo discover a prostitution ring run by chinese where underage girls are enslaved; while Isabella and Valeria manage to save Giulia, a woman mistreated by her husband, who for the love of her daughter finds the courage to report him... but for Isa, a champion of mistreated women, the real troubles begin now: on her PC, in fact, an order to stop from an anonymous but very threatening sender arrives. / Ardenzi, following the notice of investigation, appears before the judge with his lawyer and discovers that he is being investigated for incitement to suicide.

Sandro remembers that Marcello had confided in him shortly before his death that he had seen Sabatini in the company of a person who could be Bradic. Ardenzi thus begins to suspect Sabatini. While Zaccardo, having learned from the police chiefs that she will be promoted, has decided to offer her position to Claudio. / Sabella is called by Cristina in tears because her partner has returned to her and is threatening her. A drug dealer questioned by Ardenzi in prison accuses Sabatini of being corrupt. Darko Bradic's body is found and Ardenzi is increasingly convinced that Sabatini is involved in this chain of crimes.

Isabella is suspended for beating Cristina's murderer after his arrest. Sandro and Ardenzi follow Sabatini and discover that he is meeting with Lele Bianchi, a customs officer from the port of Civitavecchia already known for previous drug dealing. / Zaccardo informs Ardenzi that Sabatini will be in charge of the section. Ardenzi interrogates Lele Bianchi to try to obtain evidence against Sabatini, but before he can obtain any information, Bianchi is released from prison.

Bianchi's body is found, killed by Sabatini and thrown into the river but there is no trace of the tablet on which the drug trafficking was recorded. Claudio, who was promoted to head of the section by Zaccardo, plots to have Ardenzi removed from the police station, who is now at open war with his former friend. / Ardenzi with the help of the team decides to look for the gun used to kill Bradic, which Sabatini may still be hiding in his house. Roberto finally manages to confess to his daughter how her mother really died and their relationship is strengthened.

On the day of Valeria's and Zaccardo's wedding, he informs Ardenzi of his transfer to the Viterbo police station. The team therefore has little time to frame Sabatini: they must find the gun that killed Bradic and Clerici as soon as possible and foil the major drug trafficking that Claudio is completing with the help of Vanessa. Sandro finally discovers Sabatini's garage where the gun is kept, but this discovery could be very dangerous. / Sandro, seriously injured by Vanessa, is taken to the hospital in serious condition. Ardenzi recovers Sabatini's gun and can finally prove his guilt. Claudio, now hunted, wants to carry out the last drug trafficking and then flee abroad.

While Deputy Police Commissioner Ardenzi is obsessed with investigating his former colleague Claudio Sabatini, the Mobile Squad is engaged in a crucial operation called Mafia Capitale. A network of corruption and malpractice seems to permeate the city of Rome, and inside there is everything: politicians, entrepreneurs, fixers. Through wiretaps and investigative work in the field, the Mobile Squad is called upon to clean up.

Operation Mafia Capitale continues and this time the Mobile is targeting a paid municipal manager who manages the assignment of lucrative public contracts. To complicate matters, a man accused of his wife's murder takes Roberto Ardenzi hostage at the police station, shouting his innocence: only by helping him clear himself will they be able to convince him to surrender. In the meantime, Claudio Sabatini tries to find out who stole his diamonds.

While Roberto Ardenzi and the Mobile investigate the murder of a father, apparently the victim of two criminals, Vanessa discovers that she is pregnant by Claudio Sabatini and the former policeman sets out on the trail of the man who stole her diamonds.

While the Mafia Capitale operation returns to the forefront with the investigation into a scam in the public transport sector, the team investigates the murder of a criminal after a woman bravely provides an identikit of the killer. Meanwhile, Claudio Sabatini begins to suspect that Vanessa may have betrayed him.

Roberto Ardenzi and the Mobile have an ace up their sleeve and decide to play it to set a trap for Claudio Sabatini. In the meantime, however, a customer exasperated by the failure to grant a loan takes the entire bank hostage after stealing a gun from the security guard. Among the hostages is also Riccardo, who manages to warn the Squad.

The team is called to a test of unity after Vanessa's death, during the operation to capture Claudio Sabatini, unleashes newspapers and public opinion against them. To complicate matters, Sabatini is mistakenly convinced that his woman was killed by a police bullet, and now he seeks revenge. Meanwhile, the Mobile investigates a case of alleged kidnapping.

The investigation into Mafia Capitale returns to the forefront when the Mobile focuses on some anomalous behavior by the waste collection company. Meanwhile, Ernesto Cocco, the man who stole Claudio Sabatini's diamonds with Italo Manzi, wakes up from a coma in the hospital. Both the latter and Roberto Ardenzi are very interested in hearing what Cocco might say.

Sabatini, seriously wounded in the firefight with Manzi, is still on the run. Ardenzi knows that his former colleague will soon be on the trail of their common enemy, Guaraldi, to take back the diamonds and make him pay. Meanwhile, the Squad investigates a bank robbery, which went well thanks to a fake bomb threat.

The long-distance challenge between Ardenzi and Sabatini continues, both looking for a compromising recording that could frame Guaraldi. In the meantime, while Isabella hunts down her mysterious stalker, the Mobile continues its investigation into Mafia Capitale, discovering a case of corruption involving the Navy.

Guaraldi survived the ambush by Sabatini, who continues to interfere from afar in Ardenzi's investigations. Meanwhile, the Squadra investigates a murder case that risks turning into a private vendetta by the Chinese mafia.

While Ardenzi deals with the increasingly concrete suspicion that Sabatini has a mole at the police station, the Mobile investigates episodes of loan sharking linked to Mafia Capitale, and Isabella ends up clashing directly with her stalker.

Ardenzi managed to get away, Guaraldi was finally arrested and Sabatini is still on the run, this time in the company of Daria. But the former agent cannot give up and continues his strenuous search for the stolen diamonds. Guaraldi himself does not intend to accept defeat and plans an escape with his accomplices. In the meantime, Mauretta finds herself collaborating with the team on the case of a serial rapist, without telling her father.

While Sabatini is on the trail of Guaraldi and the diamonds, the Mafia Capitale investigation has reached a critical point: Ardenzi and the Mobile are closing in on the boss of the "middle world", the Zoppo, who operates under the aegis of the mysterious Architect. Meanwhile, the time has come for Isabella to face her stalker head-on, alone and without the support of Ardenzi and her colleagues.

Ardenzi and the Squad have managed to locate Sabatini, but they are waiting to intervene in the hope that he will lead them to another excellent fugitive, Guaraldi. In the meantime, the former official of the Services is preparing to leave the country with the shipment of diamonds stolen from Sabatini.

It's time for Ardenzi and Sabatini to show down. Alone and hunted, the former agent plays his last card: a desperate move to strike at Ardenzi's heart and force him to collaborate with him, turning his back on the Mobile and the Law.