A few scenes into 'A Prophet', something occurs, which, just in case the audience don't know what they have signed themselves up for, catapults them directly into this brutally-realistic prison drama.

Malik (Rahim) is your run-of-the-mill, 19-year-old criminal. Naïve, uneducated and jailed for a petty crime, his adjustment to life on the inside is not going well. He has already had his runners taken from him, and is now being coerced into carrying out a hit on a transient prisoner, Reyeb (Yacoubi), by the Corsican mob and its leader, Cesar (Arestrup). Malik has never murdered anyone before, however, and asks to see the warden to alert him and try and get out of it. In the daily grind of a French prison this is not how prisoners do business and the retribution that follows sets the tone for the barbarous acts which pepper the film.

Malik carries out the murder, of course, and so sets out on his way in the world of organised crime. The Corsicans, for whom he becomes a low-level lieutenant, treat him like dirt because, to them, he is an Arab. To the Arabs, however, Malik is a Corsican. And so throughout the film neither group truly accepts him - he is a loner, belonging to neither group.

Haunted by the ghost of Reyeb throughout, over time Malik learns to read and write, and even speak Corsican - all in the name of furthering his own ambitions. He does befriend, or more accurately become business associates, with a gypsy and a second inmate, Ryad (Bencherif). Through these contacts Malik slowly works his way higher and higher, becoming ever more powerful, although he is always treated as an outsider by his Corsican master.

Drug dealing, power-plays for control of the gangs - and the prison - violence and murder are never far from the surface, with the quid-pro-quo relationships that Malik cultivates always close to boiling point.

Surmised like this, 'A Prophet' sounds like anything else from the prison/mafia/gangster genre. However, it is the realism that sets this drama apart, puts it at the peak of any list of such films and is the blood which flows through its veins. Nothing is glossed over; the mundane and the macabre, the familiar and the unfamiliar - everything is presented, warts-and-all, as prison life.

A prison officer rarely makes an appearance in the film - for these are secondary characters. There is the odd scolding, or stint in solitary confinement, when Malik returns late from day-release, but no more. The prisoners cook and distribute the food, collect laundry etc and in effect run the prison.

If there is any over-reaching message from 'A Prophet' it is that crime can indeed pay. A highly cynical depiction of a prison system that is obviously defunct, the reason why 'A Prophet' works so well is that it is believable. Rehabilitation is a foreign concept. Even when Malik strives for knowledge, it is to further his criminal ambitions. Day-release is nothing more than an opportunity to cement power for the young protagonist.

Dark, uncompromising and utterly compelling - although perhaps not to the tastes of more squeamish cinemagoers - 'A Prophet' is a fascinating depiction of prison and criminal life. Approach with caution.

Padraic Geoghegan