K.O.

Bastien fights Enzo in a pro MMA bout and accidentally kills him. He apologizes, but Enzo's family Emma and Leo refuse to forgive him. Grief and guilt drive Bastien to retire from fighting and take a job at a mining facility, trying to live as far away from conflict as possible.

Two years after Bastien's retirement, the Manchour brothers crush the Andalou gang at an abandoned industrial complex. They torture Andalou to force the location of 300 kg of weed and 10 kg of cocaine hidden at the port. The attack signals the return of the Manchours' grip on Marseille.

Police Officer Alaoui warns that the Manchours are staging a comeback to take over Marseille. Her concern is questioned by colleagues Benoit and Vasseur, who doubt the urgency or viability of her claims. The debate sets the stage for a city-wide power struggle.

Alaoui receives a call from Leo, who says he witnessed the Manchours kill the Andalou gang. He warns that they will kill him if they find him, and then he vanishes, cutting contact with the police.

Emma arrives at Bastien's doorstep asking him to find Leo. Seeing an opportunity to atone, Bastien travels to Marseille and tracks down Alaoui at Hugo's place.

Hugo, beaten by the Manchours, is in the hospital and tells Alaoui about Leo's girlfriend Inaya and sister Fatou. Outside the hospital, Alaoui defeats two Manchour henchmen and is suspended for lack of evidence against them.

Leo is revealed to be Alaoui's informant, and he has information the Manchours want. He and Bastien join Alaoui to find him before Abdel and Driss can capture him.

Leo had been tipping Alaoui off about Andalou, but he witnesses Abdel kill Andalou's associate. The authorities realize Leo must be kept safe to prevent him from informing on the growing Manchour operation.

Alaoui and Bastien track Fatou to a club. There, Fatou reveals that Leo and Inaya are staying at her mother's place, guiding the search.

Canistra reviews CCTV and tracks Fatou, sending teams to Inaya's neighborhood to arrest Leo and Alaoui. A mole inside the police leaks information to the Manchours, and their goons attack Leo just before he can be moved. Bastien fights back and the police arrive to save them.

The Manchours were active years ago; they killed Alaoui's brother for protesting drug sales, burning him alive on a chair and sending the video to Alaoui. That brutal history fuels Alaoui's resolve to act now, despite police inaction.

The real reason Leo must be silenced is that he could reveal a mole in the police when he testifies. Abdel and the Manchours want to prevent any internal investigation from exposing the traitor among the cops.

Abdel and Driss lead a violent assault on the precinct, trying to spread chaos to avoid direct confrontation. Bastien, Alaoui, and Canistra fight back, turning the siege into a brutal showdown.

In the climax, Alaoui kills Abdel with a baton and Bastien defeats Driss; Canistra and several officers die as martyrs. Leo is saved and reunited with Emma and Inaya, delivering a measure of closure for those involved.

After the dust settles, Bastien admits his past guilt and decides to find a new fight for someone else. He resolves to channel his fighting once more, this time in service of protecting others and shaping a future for Leo and his loved ones.