Sentenced to six years in prison, young man Malik El Djebena (Tahar Rahim) is alone in the world and can neither read nor write. On his arrival at the prison he falls under the sway of a Corsican mafia group, led by Luciani, who enforce their rule in the prison. Malik toughens himself and wins the confidence of the Corsican group. He follows Luciani's orders to kill prisoner Reyeb. Luciani arranges 12-hour leaves for Malik, in which Luciani sends him on missions, including murder. Malik learns how to read and write, and uses all his intelligence to discreetly develop his own network. His power grows and finally he is no longer on Luciani's side.