In a near-future Paris, the government has isolated the most dangerous neighborhoods with massive containment walls. Among these is B13, a lawless area ruled by criminal gangs. Leïto, a local vigilante, becomes a target after destroying a large quantity of drugs belonging to notorious gang leader Taha. Leïto's actions provoke Taha's wrath, leading to a chain of events that engulfs his sister Lola and places both of their lives in grave danger. Desperate to save her and escape the brutal regime of B13, Leïto confronts the overwhelming power of Taha's gang.

At the same time, an elite undercover cop named Damien is assigned a high-stakes mission to retrieve a stolen nuclear weapon, which is now somewhere within B13. Damien and Leïto reluctantly form an alliance, combining their unique skills—Damien's combat and tactical expertise with Leïto's intimate knowledge of the treacherous urban landscape. As they navigate through the perilous streets and countless dangers of B13, the two must overcome their differences and work together to save Lola and prevent a catastrophic disaster.