Now in prison, Gilou makes headway as an informer and gets close to Cisco, a dangerous convict coming to the end of his sentence, who is being monitored by the police. Josephine Karlsson meets Souleymane, the 13-year-old Moroccan boy accused of the murder Laure and Ali are investigating.

Gilou is offered a way out of jail if he agrees to become a police informer, but on the condition that he keeps away from Laure. Meanwhile, the police team focus their investigation on the Paris neighbourhood of Barbès, where vulnerable delinquent minors are being exploited by receivers of stolen goods.

The police investigation screeches to a sudden halt when Souleymane disappears. How and where will they find him? Meanwhile, Laure flouts the ban on seeing Gilou, who has got himself hired as a bouncer in Cisco's nightclub. There he meets the security manager, Cisco's son Titi.

Josephine has been blackmailed by the traffickers into defending their smuggler, Maria. Ali and Laure follow whatever leads they can tease out of the new line of enquiry, but how much information can they get out of their new arrest? And is there sufficient evidence to prove a link between the international smuggling operation and the murder case they are investigating? Captain Beckriche and Judge Lucie Bordieu must find common ground - and they do.

Laure and Ali identify 'The Alsatian' and get to work on a tracking device that was hidden under his car by members of a rival gang. Josephine tries to help Souleymane but her attempts are short of adequate.

Gilou is instrumental in helping Cisco's gang acquire a stash of weapons for the upcoming heist.Laure confronts him.Meanwhile, Edelman must learn how to best act in Lola's defence

Laure tells Ali that Gilou has infiltrated Cisco's gang. To protect him, they'll need to play for time in their investigation - but their efforts are jeopardised when Judge Bourdeiou orders the arrest of Cisco's son Titi.

Joséphine heads back to Paris with young Youssef, but his brother Souleymane is now in grave danger. Judge Vargas, who was in charge of Gilou's infiltration, decides to cut his losses. But what does this mean for Gilou?

On the day of the hold-up, last minute changes cause chaos and the police's meticulously planned intervention is thrown into disarray. As the situation becomes more and more dangerous, Laure does all she can to get Gilou out to safety. But her options are limited - and very risky.