Irreversible (2002) is a remarkable, expertly crafted, beautifully tragic film by writer/director Gaspar Noé. It is the story of lovers Alex (the glorious Monica Bellucci) and Marcus (Vincent Cassel, animalistic and unhinged), and the urchins of society that they encounter one night by happenstance. Unfolding in reverse, it could be considered France's answer to Memento (2000).
One aspect that viewers will notice immediately is the nearly nonstop camera. This may leave the audience feeling nauseous at first, but it becomes more relaxed as the film progresses (or regresses). The first half hour or so may be disorienting and claustrophobic, but as we slip further into the past, things become steadier and more pleasant.
The wandering camera is indeed a character unto itself, spiraling up, over, and around the actors to create a truly visceral and cinematic experience. The entire film is meant to look like one continuous, fluid shot, and this effect is pulled off wonderfully, without even an ounce of obvious pretension. It is dizzyingly chaotic in the opening scene, but the camera quickly finds a comfortable groove.
The plot of Irreversible cannot be discussed in detail without spoiling things. Discovering who these people are and how they come to do what they do is a big part of this cinematic experience.
It should be mentioned that there is a very graphic murder within the film's initial ten minutes (the end of the story). It is so graphic, in fact, that this reviewer (who doesn't flinch when faced with Saving Private Ryan or Schindler's List) was forced to look away. Working backwards from this point, we are gradually shown the incidents that lead up to this crime. Also, be forewarned that nearly halfway through there happens a punishingly protracted scene of rape.
Though you may be disgusted at first, stay with this film to the end. You will be glad you did.