The atmosphere at Sant'Andrea is tense: Cafasso, awaiting Pietro's transfer, entrusts command of the investigation to Walter, but Pietro refuses to leave the station. Meanwhile, in Barcelona, a dangerous, ruthless drug ring is rife with bodies. Meanwhile, a teacher is injured, and the police investigate his private life, uncovering a connection to a previous murder.

Pietro, while quelling a fight on a construction site, discovers the charred corpse of a young woman: the investigators of Sant'Andrea must identify the victim with a piercing and a gunshot wound as the only clues. In Barcelona, ​​the boss Paternò, worried about the disappearance of his daughter Marina, decides to take action by leaving for the capital of Naples.

The body of a woman killed by a gunshot is found in an area frequented by prostitutes: the autopsy reveals that the victim was a nun. Matrone informs Paternò that De Giovanni ordered the murder of his daughter, so Paternò plans revenge. At Sant'Andrea the wedding of agent Santoni is celebrated, but the party ends in tragedy with a shootout.

While Commissioner Pettenella investigates who killed Paternò's daughter, Sciacca fears revenge for not having helped him. A fear that could be confirmed by the discovery of the lifeless body of a girl, the niece of an affiliate of De Giovanni. The agents are also investigating the murder of a young clerk with ties to the loan shark environment.

The discovery of a child's skeleton in a farmhouse reopens a ten-year-old unsolved case: Silla shows the evidence to Pietro, provoking an intense reaction. Despite Cafasso's opposition, Pietro decides to investigate privately. Meanwhile, Antonio and Giulia are faced with a complicated eviction that reveals a trafficking ring of counterfeit goods. In the darkness of his search, Sciacca desperately searches for his missing woman, ignoring the rules to save her life.

A boat explodes, carrying the body of an old sailor onto the reef. The initial hypotheses of an accident are discarded by the autopsy: it could have been an attack. Sciacca, worried about Silvia, asks Pettenella for help. Cafasso presents Sciacca with a choice: if he wants to continue following the case, he must accept Ramaglia's supervision.

A woman is unable to enter her apartment. Demetrio and Giulia find her husband dead, apparently struck by lightning. Sciacca, devastated by Silvia's death, is removed from the investigation and the only person who manages to reach him, despite his desperation, is Pettenella, the most cynical of the men of Sant'Andrea.

The death of a seventy-year-old woman found in her apartment leads Antonio and Francesco to investigate. Meanwhile, Cafasso, to avoid leaving Sciacca to the ghosts of the past, entrusts him with the management of the archive. A complaint for vandalism leads the agents of the Squadra to discover an illegal traffic of disability permits.

A fire due to an explosion in a building causes the death of a woman and scares Lepre to death, who fears a plot against him. Pettenella tells Sciacca that Bonanno is willing to collaborate, but Salvatore is convinced that it is all a bluff. Ivan manages to escape and, despite being wounded, reach Tania, who, confused, confides in Stefano.

The son of the PM Menale mysteriously disappears and the team suspects a criminal sentenced by the magistrate, who has just escaped from prison. In the meantime, at the foot of an abandoned farmhouse, the body of a girl with traces of lethal chemical substances is found: with the help of Dr. Salibra, the men of Sant' Andrea try to understand what happened. Pettenella takes over the management of the police station in the absence of Cafasso, who left for the East. After a night with Berti, Anna is in internal conflict and decides to follow her instinct.

After a failed ambush, De Giovanni is in the hospital seriously injured; his clan, determined to take revenge, exterminates the family of Matrone's right-hand man, unleashing a war. A woman sees the killers, but while running away she loses a shoe that will become crucial to the investigation. At the same time, a theft of precious coins and the disappearance of Fernando Vacui further complicate the situation.

Francesco and Demetrio find the body of a woman in the trunk of a stolen car, with no correspondence in the missing persons reports. The case thickens when the body of a boy is also found: the only clue for the men of Sant'Andrea is a portrait with the stamp of an art academy. A new agent, Laura Rotunno, joins the Squad. In the meantime, the murderer of Paterno's daughter dies in prison.

With Cafasso's return from the East, investigations reveal that the Camorra was using a Chinese port to export toxic waste to Asia. Alfio and Patty, taking a short vacation, suddenly end up in the delivery room.

After the death of the mafia boss Paternò, the Sant'Andrea department faces new challenges: Inspector Claudio Martusciello captures a drug addict who robbed an elderly woman, but does not appear in court to testify. They discover that someone has taken his identity. In the meantime, a headless man is found and a Somali girl mysteriously disappears. The mother confesses to having hidden her to save her from infibulation, but the child has disappeared. Francesco Silla, seeing his father with another woman, decides to leave his grandfather's house in Piazzetta Viviani.

A medium reveals to the press the location of the body of a businesswoman who has been missing for two years at the bottom of a lake. Her husband, with photos taken by a diver, asks to reopen the case. Cafasso and Pettenella find the car and the body in the indicated location. The autopsy excludes drowning, confirming murder. The investigation focuses on the victim's family and collaborators, revealing a complex picture of rivalries and tensions that include a fired employee, her husband and children.

Following a tragic car accident, a man's body is pulled from the wreckage. Initial investigations reveal that he is Matarazzo's assistant. When he returns home, the detective finds his apartment in disarray and receives a threatening phone call. In another story, Francesco discovers the involvement of a friend's brother in a theft with a particular motorcycle. Meanwhile, Anna continues to lie to her husband to hide a secret relationship.

A boy is beaten bloody by some thugs who disappear into the night. A friend promptly helps him but the two have placed a bomb in a construction site to prevent its construction. A full-scale investigation begins and Pettenella discovers that the engineer in charge of the project hides a not-so-sharp past. In a supermarket parking lot Giulia witnesses an accident involving two elderly people, the perpetrators of an alleged deception.

An engineer and a no-global protester lose their lives in a deadly ambush. Ramaglia, who rushed to the scene, is suspected of shooting the protester, sparking urgent investigations to establish his responsibility. The Squadra investigates the involvement of the engineer and the possible instigators, with the Camorra as the main suspect. The discovery of an architect's body mysteriously links the victims. Francesco settles in Piazzetta Viviani, while Anna seeks justice for her sister's death.

A manager of an armored car agency surprises three robbers in his kitchen who threaten to kill his wife and daughter. After emptying the safes, the criminals flee. The Squad intervenes promptly, finding the family unharmed in their garage. Meanwhile, a graphic design studio reports a murder and a gas station reports a mysterious disappearance, linked by traces of blood that lead to new disturbing discoveries.

The Squad investigates the death of a missing girl, found in the woods. Was it an accident or a murder? The autopsy reveals a miscarriage as the cause of death. Who was the girl? Who were her friends and the person responsible for the pregnancy? Michele Paglietta, her boyfriend, denies killing her. Sciacca, watching videos from a gas station, notices a suspicious blue station wagon among the parked cars.

The Squad continues the investigation into the death of Patrizia De Simone. Antonio and Demetrio go to the home of Domenico Grandi, who is lying face down on the ground. Next to him, a gun. Meanwhile, the body of an unidentified sailor is found at sea, with only a photo of a young girl.

Dr. Miriam Girelli, a famous notary, calls Sant'Andrea confessing to having killed a thief in self-defense. Walter, Sciacca, Nicoletta and Dr. Mari find the body in the villa with a necklace and a gun next to it. The husband reveals that the victim was a member of the squash club. There are no signs of forced entry, but the thief has disappeared from the security footage.

A new mix of cocaine and chemicals is tested on regular users. Sciacca, Laura and Dr. Salibra interrogate a dealer to get the name of the supplier, but without success. Alfio receives a dose of cocaine and a note with a sequence of numbers and letters that Walter and Anna discover to be the code for a container with 100 kg of cocaine for the boss Annibale Ruotolo. Kevin Inzerillo, an old acquaintance of Salibra, is involved. The doctor decides to investigate on her own.

Synthetic cocaine invades Naples. Santo Cosenza, linked to trafficking, has disappeared, jeopardizing the confrontation with the boss Annibale Ruotolo. Pettenella's phone, authorized for control, is not giving signals. Adrianne Ledger, under investigation, has disappeared; Cosenza's fingerprints in her apartment provide a lead. Sciacca, Anna and Demetrio investigate a robbery that took place in a villa where drugs were found.

The Squad continues the hunt for Adrienne Ledger. Inside a refinery they find a charred corpse with clues that seem to link the accident to Annibale Ruotolo, but the investigations lead to discover that it is a red herring. A boy with a small criminal record for drug possession is found dead. The victim knew Dr. Salibra's son. Antonio investigates the disappearance of a student in Tirana who may have come to Italy for a relationship with a student from Naples met in chat. Pettenella, for the first time, feels the weight of responsibility on her shoulders and runs away, avoiding any meeting with her nephew Joe.