One of the appealing tricks of film is its ability to reverse time. Simply run the reel in reverse and every unhappy ending is undone. It’s just one of the wish-fulfilling features of the medium, though little used compared, for example, with film’s indulgence in revenge fantasies. In Irréversible, Gaspar Noé combines the two traits into a brilliant, brutal assault that builds from simpleminded sensationalism to profound formal beauty. Along the way, Noé challenges preconceptions about the nature of time, free will, and guilt and innocence, transgressing the bounds of good taste and decency while implicating us in the voyeuristic violence and obscenity. No wonder this is the most controversial and reviled film by a director already notorious for the graphic brutality of 1998’s Seul contre tous/I Stand Alone.

In Irréversible, shocking subject matter comes bolstered by a formal assault and troubling æsthetic and philosophical inquiry. Contradicting its title, the film tells its tale backward, starting with a scene shot in a Dantesque red-lit S&M club called the Rectum (giving new meaning to the old joke " Rectum? It damned near killed him! " ), with the camera careering like a pinball ( " unsteadi-cam " ?) about the debauched naked souls seeking release. The camera mirrors the mood of Marcus (Vincent Cassel), a frantic, mostly off-screen presence who’s after someone named Le Tenia (Jo Prestia). A companion, Pierre (Albert Dupontel), appears to be the restraining voice of reason. But when Marcus gets the worst of it in a fight with someone who breaks his arm and is about to rape him, Pierre comes to his aid.

Not that Noé allows us much relief in this rescue, as it involves a prolonged act of violence compounded in its repulsiveness by the nauseating camerawork and soundtrack (a mechanical drone that sounds like chanting monks undergoing torture). The sequence calls to mind the conditioning undergone by Alex, the protagonist in Stanley Kubrick’s A Clockwork Orange, to cure him of his taste for violence. In addition, placing the act at the beginning of the film dispels any satisfaction you might get from it as revenge for the grotesque crime that spurs Marcus to his vendetta.

That doesn’t diminish that crime’s awfulness, however, and like a diabolical fusion of Straw Dogs and Memento, the film retreats, scene by scene, to the bowels of the pedestrian tunnel where another Alex (Monica Bellucci) has her encounter with Le Tenia — the tapeworm, the resident demon in this reverse tour of the gastric tract of time. Midway through the ordeal a figure enters the background, takes one look, and beats it. Lucky him, but we get no more relief here than we did in the Rectum, for the camera has now stabilized, and it remains motionless as the violation goes on and on and on.

What’s the point? If nothing else, the film makes it clear that the impulse to unprovoked, brutish cruelty and the subsequent reaction of righteous revenge end up in the same place — in the Rectum. Both drives result in the same shit. The film also toys with the characters’ unconscious involvement in their own victimization. Pierre, a philosophy teacher and Alex’s ex, banters in various scenes with Alex and Marcus about her new lover’s animal prowess and Pierre’s inadequacy and cerebral detachment. He passive-aggressively goads Marcus into some bad behavior at a party and a nasty argument that leads to the catastrophe. Under a social façade, issues of manhood, jealousy, repression, and homophobia seethe, and they erupt with terrible consequences by the end.

Or the beginning. The reversed chronology may be just a gimmick, or it may be an attempt to comprehend time, to transcend it and its consequences, however briefly, through the illusion of film. Moments of bliss balance the moments of horror. Marcus and Alex awake naked in a gold-lit boudoir. She has had a dream, and later (or earlier), she’ll relate it to a book she’s read that claims that the future is already written, hence the existence of premonitory dreams. Posed before a poster for 2001: A Space Odyssey reading " The ultimate trip, " Alex smiles: she’s young, beautiful, in love and pregnant. No wonder the already written future seems to her as shimmering and hopeful as the radiant final shot of the film.

" Time destroys everything, " a character says at the beginning — or is it the end? — of Irréversible. Having been through it all, he may well know best. But films like this are a way of fighting back.