A nuclear weapon has been stolen by the most powerful gang in Paris' treacherous, walled-in ghetto, and it's up to a determined cop and a vigilante criminal in search of his sister to infiltrate the sector, save the girl, and get the bomb out of the bad guys' hands in an action-packed tale produced by Luc Besson and directed by cinematographer Pierre Morel. The year is 2010, and a massive wall has been erected to keep the violence of the Paris ghetto confined to District B13. Within these walls, gangs rules the streets and law enforcement is powerless. This time the gangs have gone too far, though, and when the authorities realize that a nuclear weapon has been smuggled into the district, specially trained policeman and martial artist Damien is assigned the task of retrieving the weapon of mass destruction before Paris goes up in flames. He's not going to be able to do it on his own, though, and when Damien learns that breakaway bad guy Leïto's sister has been abducted by the very same gang, the pair soon forges a tentative partnership that merges the power of law enforcement with the anything-goes attitude of the criminal element.
by Jason Buchanan synopsis