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.