In 2010, social problems such as violence, drugs and organized crime have overrun the poorer suburbs of Paris, especially Banlieue 13, commonly referred to as B13, a ghetto with a population of some two million. Unable to control B13 the authorities construct a high wall topped by barbed tape around the entire area forcing the inhabitants within to survive without education, proper utilities or police protection behind the containment wall. Police checkpoints stop anybody going in or out.
Three years later an almost feudal system has developed amongst the street gangs of B13. The area is now flooded with hard drugs such as heroin and completely controlled by gangsters. Certain blocks are ruled over by various transsexuals and one high rise apartment block is looked after by an athletic and street-wise man known as Leïto (David Belle). Leïto hates drugs and injustice and wages a one-man war against a neighboring gang lord named Taha Bemamud (Bibi Naceri) to keep his own building and people safe and free of drugs. Leïto captures 20 kg of cocaine from Taha, worth over a million euro, which incites Taha to send his thugs to recover the merchandise, led by the towering K2 (Tony D'Amario). Leïto destroys the cocaine by using bleach and uses parkour to evade Taha's thugs through the building and across rooftops.