Three years after the original film, law and order efforts in the ravaged District 13 have yielded little success. The death of gang overlord Taha Ben Mahmoud has created a power vacuum, leading to a brutal struggle for dominance among five rival gang lords, all vying for Taha's throne. Meanwhile, Leïto tirelessly attempts to tear down the walls enclosing the district, yet he is thwarted by Molko, an African gang lord who believes the walls are essential for protecting the area from external threats.
In another corner of the district, Damien confronts a major drug dealer, eliminating him with impressive skill. However, things take a turn when Damien is framed for drug dealing and subsequently arrested. Under dire circumstances, he manages to make a desperate call to Leïto for help.
The Department of Internal State Security (DISS), under the corrupt leadership of Walter Gassman, has sinister plans to demolish the central tower blocks in District 13 with precision bombing, aiming to replace them with luxury apartments. To instigate chaos, the DISS orchestrates the killing of two policemen, leaving their car in District 13 to create the illusion that gang members were responsible for the deaths. This fabrication convinces the French President to authorize a strike against the district. However, a teenager named Samir captures the DISS's crime on camera before he and his friends are apprehended, but not before Samir manages to slip his memory card to Leïto.
Determined to uncover the truth, Leïto allows himself to be arrested to infiltrate the prison where Damien is held. Together, they hatch a plan to expose the DISS agents. While Damien distracts the guards, Leïto bravely breaks into Gassman's office to retrieve crucial evidence.
On their return to District 13, the duo rallies the gang lords—Tao, Molko, Little Montana, Karl the skinhead, and Ali-K—to unite against the impending destruction of their home. As tensions rise, the President contemplates the devastating choice to obliterate District 13 even after its evacuation. The situation escalates when gang members storm the Élysée Palace, confronting the President and presenting the evidence that Gassman is indeed corrupt. The stakes heighten as Gassman takes the President hostage in a desperate bid to push for the demolition.
Ultimately, Leïto, Damien, and the gang lords manage to save the President and subdue Gassman, earning the President's gratitude along with a commitment to fund the restoration of District 13.
In the aftermath of conflict and with the neighborhood now empty, the gang lords decide that rebuilding District 13 from scratch is the way forward rather than merely repairing its remnants. The film concludes with a dramatic scene of the district’s buildings being demolished, while the President, visibly relieved, quips that he could use a drink.
In a light-hearted post-credits scene, we glimpse the President enjoying camaraderie with the gang lords, along with Damien and Leïto, sharing laughs and cigars as they reflect on the events that unfolded.
