An awful, AWFUL Gaspar Noé movie from 2002.
By awful, I don't mean the movie is poorly lensed, terribly directed, or acted in a way that evokes laughter.
Let me pause now to say that there are spoilers ahead.
The story's told backwards - the scenes are in reverse chronological order. We see the final scenes first, and then the story fleshes out more as the scenes prior reveal more about just how horrible the ending is. You'd think that this storytelling technique doesn't make sense or would fall flat - after all, if we know "what happens later", it makes what "happens before" less interesting, because we know where the story's going. But this isn't a movie where the narrative is about a plot, or you're particularly concerned with plot details. Relatively quickly you have a rough idea of where the plot is going.
The ending is this - Captain Friendzone, who's always wanted to have sex with the beautiful female lead and been the third wheel to her and her boyfriend is taken away by police to spend the rest of his life in prison. He has taken her rape harder than her boyfriend did, and savagely beat the perpetrator to death with a fire extinguisher. At first we have no idea why the two men are chasing "The Tapeworm" to an S&M gay bar, or why the man meets a grisly end.
But as the movie progresses, not only do you see how a tragic set of circumstances one after the other lead to this end, we see just how awful this kind of story plays out. The first thing we're robbed of is the grim satisfaction of knowing justice was served - the fact is that the man beaten to death isn't the man who actually raped the girl. So Captain Friendzone's heroic sacrifice was in vain, and the bad guy gets away with it.
The savage rape is due to her walking to The Metro to take the subway home, and walking in on a pimp savaging a prostitute. He decides to rape her anally for a scene that goes on far too long. A bystander happens by, but instead of the movie trope of the bystander's presence stopping the assault, real life writes this script - the man hurriedly runs away, not wanting to be involved. Her baby dies, and her own condition is failing.
She's walking home because of a silly fight between her and her boyfriend. The one whose baby she is going to have.
And yes, as the story moves on and on and on, we learn more about the characters, become more emotionally invested in them, and the later details of the bad things that happen to them, and just how fast things can go from happiness to tragedy.
Ironically, "Irreversible" has "a happy ending" - we start off with a half dead woman, a man in handcuffs and another man lying dead in a pool of his own blood and teeth. We end up with a happy couple learning and overjoyed they are about to have a baby. But having learned in advance what happens, we can take no joy whatsoever in the lightening of the mood, the more happy circumstances that play out on the screen, and wonderful times. Each new revelation about their happiness, their hopes and dreams, one fatal decision here, another unfortunate choice there - we cannot enjoy mundane things anymore because we have learned the result. It is a work of absolute genius.
Like most Noé movies, which weren't box office smashes or art house darlings, this was a work of brilliance by an auteur who likes playing with story structure and writing a story that's more about mood and telling a meta-narrative over an actual narrative. This was more successful than his more adventurous meta-narrative, Enter the Void. But it is an absolute masterpiece of moviemaking, one that got rave reviews and rightly so. The fact that it is a heartwrenching, gut-punch of a movie - more so at the end than at its ultraviolent beginning, makes it hard to watch and harder to rewatch.