The following review contains spoilers.
In the supplements on the Criterion edition of Harakiri (which I reviewed for Battleship Pretension (plug!)), screenwriter Shinobu Hashimoto provides some insight into why his flashbacks are so effective, noting that "it isn't a flashback if it moves in the direction of the drama." Each of the flashbacks is "introduced" by an important dramatic turn or a new question. Also, there are people in each scene as clueless about the story Hashimoto is about to cut to as we are in the audience. Each time, we get a dramatic, emotional reason for diving into the past to illuminate the present.
And this is the key to what's missing in The Skin I Live In. Almodóvar begins with a fascinating set-up. Robert Ledgard (Antonio Banderas) is a brilliant surgeon researching a new type of artificial skin, which he's testing on a patient, Vera (Elena Anaya), who also seems to be his prisoner. Their relationship is intriguing, as Vera seems to want him desperately while Robert is constantly battling his own attraction towards her. The film's best image is classic Almodóvar - Robert spies on Vera through a camera, which he views on a plasma screen as big as his wall. Before long, a crook will break into their house and rape Vera, with strong implications that they used to have a relationship. She tosses out a line that feels revealing even before we know the context - "I've had enough of sex in the garden" (or something to that effect).
Even better, the answers to all of these questions are thematically satisfying, emotionally shattering, and quietly terrifying, but their presentation is so ham-handed and obvious, bereft of true dramatic impact and stuffed into a flashback that serves no structural purpose.
The key revelation is that Vera was once Vincente, a wayward, pill-addicted twenty-something who raped Robert's daughter, Norma, sending her spiraling into insanity and eventually killing herself. Upon hearing about the rape, Robert kidnapped Vincente and locked him in a dungeon, before performing on him a forced sex change (the result of which leaves him looking very similar to Robert's late wife, who ran away with her lover, was burned in a car crash, and eventually committed suicide) and keeping her prisoner for further experimentation. Which, by the way, is an awesome story, but even the best concept goes sour when mishandled.
The flashback itself is totally unmotivated. Robert and Vera have sex, and then each seems to dream, or at least reflect upon, about how they met. First, we see Robert's perspective of a wedding he and his daughter attended, and how he found his daughter lying in the garden unconscious, clearly the victim of rape. Then, Almodóvar cuts back to the present, gives us an isolated shot of Vera asleep, and fades back into that same night to show her perspective. But her flashback doesn't start there - it starts in Vincente's mother's vintage clothing store, in which Vincente and another woman work. We know right away, because of the principles of cinematic language, Vera has to be one of these two people. But then Vincente attends the wedding alone, and suddenly the whole movie opens up in front of us - Robert kidnapped Vincente and locked him in a dungeon, before performing a forced sex change on him and keeping her prisoner for further experimentation. And yes, I know I already typed that sentence, but only as a means of pointing out how redundant the film becomes, because the next ungodly amount of time is showing step-by-step how this is carried out, and the whole affair starts to feel a lot like the last few episodes of Lost - lots of answers without any emotional heft.
The key problem here is that all of the characters already know the whole story. We're kept in the dark because it's more surprising that way, but as a result, we're on a totally different trajectory than the characters. We don't get any time to truly appreciate Robert's struggle, because by the time we move back to the present, he's made up his mind - Vera goes free, and they're going to live together and have lots of creepy sex. Vera, despite her promises, eventually turns on him, killing Robert and Robert's mother/housekeeper. But her struggle, her chess game, is kept totally secret until a few seconds before that particular showdown.
So we can reflect on the earlier, more intriguing part of the movie, and apply the twist in order to gain some emotional resonance, but it's unnatural, unearned. We're being manipulated, saving the film's most intriguing element for a revelation that operates as a twist. But unlike the twists in Memento, Fight Club, Psycho, or any of the other classics of "gotcha!" cinema, it's not used to mirror the characters' emotional journeys. It's used cheaply, and elaborated on unnecessarily, when time could have been spent with the characters and what all this has meant to them. Instead, by the time we cut back to the present, everyone seems pretty content. Until suddenly they're not. Couldn't we have gotten a hint of Vera's plan? Wouldn't that have been more emotionally satisfying, never mind the heightened dramatic intrigue. Couldn't we get a moment of Robert wondering what kind of monster he has become, or maybe an indication that he believes he's earned his monstrosity after the tragedies that befell him? Or maybe he's too completely lost in his own obsession and madness to even think these things. We never know.
I'm left wondering just what this movie was trying to do, exactly. If it's yet another contemplation about how an urge for revenge manifests itself in worse acts than that which it's avenging, fine, but by the time we meet Robert, it's already clear that whatever he did to Vera was far worse than anything she could have done to him. Robert's plight remains distant, unknowable to us; he's a monster when we meet him, and the unfolding revelations only help us to understand, but never sympathize. Meanwhile, save for one glorious moment in which she discovers yoga, we never really see Vera for who she is until the final minutes of the film. The last scene, in which she reunites with her mother and the other girl in the shop, is similarly backwards - because of the events shown in the film, it makes narrative sense for Vera to reveal herself to the shopgirl first, but the true emotion should remain between Vera and her mother, and we're only given a slight hint of that.