While Deputy Commissioner Ardenzi is obsessed with the investigation into his former colleague Claudio Sabatini, the Mobile Unit is launching a crucial operation called Mafia Capitale. A network of corruption and malfeasance appears to permeate the City of Rome, involving politicians, businessmen, and fixers. Through wiretaps and field investigations, the Mobile Unit is called in to clean up the mess. Ardenzi is now certain that Sabatini has returned to Rome and is trying to close the loop on him. For his part, Sabatini must resolve a major situation: he staked everything on a shipment of diamonds, and now someone has stolen them. Meanwhile, the Mobile Unit is working on the case of a young woman who was raped, and wiretaps continue in the Mafia Capitale investigation.

Operation Mafia Capitale continues, and this time the Flying Squad's target is a paid municipal official who oversees the awarding of lucrative public contracts. Complicating matters, a man accused of his wife's murder takes Roberto Ardenzi hostage at the police station, proclaiming his innocence: only by helping him clear his name will they be able to convince him to surrender. Meanwhile, Claudio Sabatini tries to find out who stole his diamonds. While Roberto Ardenzi and the Mobile Squad investigate the murder of a father, apparently the victim of two criminals, Vanessa discovers she is pregnant by Claudio Sabatini, and the former police officer sets out to find the man who stole her diamonds.

While Operation Mafia Capitale returns to prominence with its investigation into a public transportation scam, the team investigates the murder of a convicted felon after a woman courageously provides a sketch of the killer. Meanwhile, Claudio Sabatini begins to suspect that Vanessa may have betrayed him. Roberto Ardenzi and the Mobile Squad have an ace up their sleeve and decide to use it to set a trap for Claudio Sabatini. Meanwhile, however, a customer, exasperated by a loan refusal, takes the entire bank hostage after stealing a gun from the security guard. Among the hostages is Riccardo, who manages to alert the Squad.

The team is called upon to demonstrate their unity after Vanessa's death, during the operation to capture Claudio Sabatini, sparks a backlash among the newspapers and public opinion. Complicating matters, Sabatini has mistakenly convinced himself that his wife was killed by a police bullet, and now seeks revenge. Meanwhile, the Mobile Squad investigates a suspected kidnapping. The Mafia Capitale investigation comes to the forefront when the Squad uncovers some unusual behavior by the waste collection company. Meanwhile, Ernesto Cocco, the man who, along with Italo Manzi, stole Claudio Sabatini's diamonds, awakens from a coma in the hospital. Both Cocco and Roberto Ardenzi are keen to hear what Cocco might say.

Sabatini, seriously wounded in the firefight with Manzi, is still on the run. Ardenzi knows his former colleague will soon track down their mutual enemy, Guaraldi, to reclaim the diamonds and make him pay. Meanwhile, the Squad investigates a bank robbery, carried out thanks to a fake bomb threat. The long-distance battle between Ardenzi and Sabatini continues, both searching for a compromising recording that could incriminate Guaraldi. Meanwhile, as Isabella hunts down her mysterious stalker, the Mobile Squad continues its investigation into Mafia Capitale, uncovering a case of corruption involving the Navy.

Guaraldi has survived Sabatini's ambush, and he continues to interfere in Ardenzi's investigation from afar. Meanwhile, the Squad investigates a murder case that threatens to escalate into a private vendetta by the Chinese mafia. While Ardenzi contends with the growing suspicion that Sabatini has a mole at the police station, the Mobile Unit investigates loan sharking incidents linked to Mafia Capitale, and Isabella ends up directly confronting her stalker.

Ardenzi has escaped, Guaraldi has finally been arrested, and Sabatini is still on the run, this time accompanied by Daria. But the former agent refuses to give up and continues his strenuous search for the stolen diamonds. Guaraldi himself refuses to accept defeat and plans a prison break with his accomplices. Meanwhile, 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 Flying Squad are closing in on the boss of the "underworld," Zoppo, who operates under the aegis of the mysterious Architect. Meanwhile, the time has come for Isabella to confront 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 holding off on intervening, hoping he will lead them to another high-profile fugitive, Guaraldi. Meanwhile, the former intelligence officer is preparing to leave the country with the shipment of diamonds stolen from Sabatini. It's time for Ardenzi and Sabatini to face their fate. Alone and hunted, the former agent plays his last card: a desperate move to strike at Ardenzi's heart and force him to cooperate, turning his back on the Flying Squad and the law.

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.