Malik el Djebena (Tahar Rahim) is a petty criminal who has just received a sentence to prison. He a nineteen-year-old of North African origin who is not a Muslim. Malik is very apprehensive as he enters a dark new world that he knows nothing about but senses will be dangerous and mysterious. Given a cell of his own, he tries to hang out by himself. But Cesar Luciani (Niels Arestrup), the wily and combustible head of the Corsican prisoners, orders him to murder an Arab inmate (Hichem Yacoubi) in exchange for protection from tough guys of all stripes in the prison. Desperate to get out the predicament, he tries to contact the warden and discovers that Luciani has guards under his power. There is no way out and so Malik kills the Arab, who then turns into an otherworldly presence who remains with him as he faces new challenges.

Luciani takes him under his wings much to the consternation of his Corsican buddies who view this young man as nothing more than "a dirty Arab." Malik handles odd jobs for the boss and takes a course where he learns to read and write. He is given a new cell with conveniences such as a TV and a small refrigerator. Luciani is so impressed with him that he arranges for Malik to be granted day-long leaves during which he serves as a middle-man for his boss's many criminal operations. At the same time, this young man becomes more aggressive and sets up a drug operation with Ryad (Adel Bencherif), a former inmate who is now his best friend.

A Prophet is co-written and directed by Jacques Audiard who has succeeded in making a gritty and tough prison drama which registers on the senses and the mind as an insightful study of power. It illustrates the irony that crime is seeded and carried on within prison systems everywhere. Although newcomer Tahar Rahim does a good job as Malik, it is Niels Arestrup's performance which stands out: his Luciani is a wily, nasty, and treacherous man who one minute commends his protégé and the next, humiliates him in the most shameful way. He uses Malik yet at any moment is capable of throwing him away. In the prison milieu and on the streets of Paris, the survival of the fittest holds sway.