Four weeks after giving premature birth to Romy, still in an incubator at the hospital, Laure Berthaud is eager to resume service. The 2nd DPJ is called in the twentieth arrondissement where a human torso was discovered. Arnaud Beckriche, the new Commissioner, overseeing the investigation, leaves a week to his team to solve the case before transferring it to the criminal brigade. For her part, Josephine languishes in a firm specializing in business law when Eric Edelman comes to offer to defend the son of a famous cosmetic surgeon, accused of having ordered the murder of his father.
The torso has finally been identified: the victim was a policeman, a member of Bac Seine-Saint-Denis. On the spot, Gilou and Laure find the Commissioner Herville, their former superior. He informs them that a survey of the IGPN, investigated by Judge Roban, targeted the deceased's team. In another case, the mysterious death of Nicolas, the magistrate discovers that the young man and his roommate were paying off their charms. The trial of Thomas Weber, the son of a famous surgeon, begins.
The interrogation of the Camara brothers does not allow Laure to move forward, but Brémont informs him that his informer told him that Drissa and Bakary had taken part in a burglary, without the stolen gold being found. Josephine wakes up under a bridge, convinced she has been raped. She asks Laure for advice but categorically refuses to lodge a complaint, which could be detrimental to her career. Roban contacts Marianne because he wants to see her. At the trial, Rudy revisits his version of the facts and charges Thomas Weber.
Despite the strong objections of Beckriche, Laure, Gilou and Fromentin are convinced that they must stay on the trail of the Camara brothers. They discover that their homework is only a facade, behind which lies a traffic of contraband cigarettes. In the field, Gilou confesses the whole truth to Laure about the bullion. For his part, Tintin has to deal with the arrival of his son Ruben, who came to spend a few days with his father. In addition, Laure's investigation into Josephine's rape is progressing.
The body of a teenager is found in the rubble of a building. Warned by Herville, Laure is convinced that there is a link with the investigation into the murder of Mercier and is trying to recover this case. In parallel, she continues her investigations to shed light on the rape of Josephine. Furthermore, the ex-wife of Fromentin is worried because she is unable to reach their son. The panic spreads to the policeman because Ruben does not answer his multiple calls either.
Jean-Etienne Vern asks for Josephine's help because he is summoned for a conciliation commission: Stéphanie, a former partner, declares the breach of her contract and accuses him of harassment. At the police station, Enzo's interrogation of Justine sets the police on the trail of Maria, the girl's best friend. Laure and his colleagues are trying to find young Roma but she no longer comes to college.
The fiasco of the search of the Roma camp leads the police to resume the investigation of the Bac. Arnaud Beckriche asks Laure and his colleagues to focus their efforts on Jolers and Calvi to establish the extent of corruption. Herville has confirmation that one of his men has warned the mayor of the operation to make it fail. To appease her revenge, Josephine takes action. In addition, Romy's health is improving.
The surveillance of Calvi and Jolers confirms that they are in touch with the Camara brothers. Beckriche is asking for additional resources for his team and categorically refuses to allow the IGPN to resume the investigation on its own. For his part, Roban receives the results of his brain biopsy. Joséphine starts working alongside Edelman and is interested in the Bodin file. She is, indeed, intrigued by Roban's findings, that she has been more meticulous in her work.
Cars burned, vandalized bus shelters: anger is brewing in the city after a police blunder. The population thinks the police have abused their authority and used violence inappropriately. Some take advantage of the confusion to stir up trouble in the streets. Chaos is not far off. The prefect makes the point with the commissioners Herville and Beckriche and prohibits any questioning so as not to cause more riots. The extremely tense situation causes the Calvi to panic, while Jolers keeps a cool head. He intends to take advantage of the situation of Drissa Camara, who is at bay.
Fabienne Mangin submits a modified plan to the City Council so that the land where the Roma camps were would be zoned as buildable. Having not obtained satisfaction, Drissa Camara is more threatening. For her part, Laure tries to find Maria and convince Herville to search for the vehicle of Calvi and Jolers. As for Josephine, she lets go of nothing and subpoenas Judge Roban and Attorney Machard to appear. Edelman fears such action will hurt his practice.
Arrested, Drissa Camara asks to see Gilou and offers him recordings involving Calvi and Jolers in the murder of Mercier. He is willing to give them to him in exchange for an agreement to reduce the charges against him. Josephine receives a summons. Tintin tries to understand the failure of spinning and checks the images of surveillance cameras at a service station. Moreover, the presiding judge asked Judge Roban to undergo a medical examination.
The medical committee renders its verdict, declaring Judge Roban unfit. Relieved of his duties, he must pass all files to colleagues. For their part, Laure and Gilou interview Dr. Couderc, a doctor in contact with Moldovan. The latter is not found, Jolers is questioned again, without result. In addition, a flaw in the proceedings prematurely ends the police officer's detention. Finally, little Romy can finally leave the hospital.