Paris, 2010. An isolation wall surrounds the ghetto cities of District B13. Within these walls, without effective law enforcement, gang rule is absolute. Damien is a member of an elite police squadron, highly trained in martial arts. He goes undercover to infiltrate a gang in order to defuse a neutron bomb and save District B13 from annihilation. Damien recruits the help of a criminal named Leïto -- whose only goal is to save his sister from the clutches of the same gang.