Battle in Heaven (18)

You may have got the wrong idea about the film from the adverts, which show the top half of a beautiful, naked young girl lying on white sheets. The image is dishonest: true, you do get to see the girl naked, but what the posters don't show is that she is lying next to a fat, middle-aged man whose penis, black and stumpy, is slowly wilting. If you're so minded, I suppose that's a bit saucy; but the impression is not of voyeurism, more a detached but tender curiosity, and it would take some effort of will to be either aroused or disgusted by it.

It would be even harder to get aroused by another scene in which Marcos, the fat man, is shown having sex with his even fatter wife. You see the folds of flab hanging off them both, the sweat and hairiness on her as well as him; and as they separate you get a glimpse of her buttocks, thickly rivered with black veins. It is not pretty, but it is moving.

Apologies if you don't want to read about this sort of thing; but I would hate people to go to the film on my recommendation, not knowing what they were letting themselves in for. And sex lies at the heart of Reygadas' film, which is concerned - or this is how I took it - with the ways in which our thoughts and longings are shaped by and expressed through our bodies, and how far they can transcend them. The action takes place over a weekend in Mexico City. Marcos works as a driver for a general, though his principal duty seems to be chauffeuring the general's gorgeous, spoiled daughter to and from the "boutique" where she and her rich friends indulge in a little light prostitution. Marcos's wife, whose name we never learn, scrapes a living selling alarm clocks and nasty-looking cakes at an underground station. On the Friday morning, a baby they have kidnapped has died; as the weekend goes on, remorse pushes Marcos to even greater sins, and then to repentance.

Why this kidnapping has happened and how the baby died are never explained; but this gap is one of the film's most exhilarating features. Nowadays, Hollywood is addicted to back-story. Every serial killer, every bad parent, every mad chocolate factory-owner gets a flashback or a monologue to tell us what made them turn out this way - as if people can be explained (and therefore forgiven). In the real world, though, explaining a person is like explaining a rain storm: you can account for it in general terms (the sun makes the water evaporate off the sea, changes in air pressure make the wind blow), but could you ever show a particular storm's back-story? Reygadas never tries to explain his characters: Ana's whoring, the kidnapping of the baby, Marcos's acts of destruction - all remain puzzles. But even though nothing is explained, everything is, it seems, forgiven. By the end, Marcos - a brilliantly deadpan performance - has committed acts that are, by any objective measure, evil. And yet it is hard to feel that he is anything but a good man.

This sense of redemption is accomplished by the simplest means - the way the camera moves, the swell and hush of sounds. At times you think you are seeing things from Marcos's point of view, but then you catch sight of things he can't possibly be seeing. Early on, as Marcos and his wife discuss the baby in the station, the camera is continually distracted by passers-by, drifting after them until they round a corner or another commuter catches its attention. Sounds - the clicking of shoes on a pavement, the shouts of children - boom then fade inexplicably; at a petrol station, Bach plays over the chanting of pilgrims - you think it is the soundtrack, but then it turns out that the characters in the film can hear it too. The effect is to detach the film, ever so slightly, from reality - to make you feel that you are sharing an alien view of humanity, affectionate, remote, all-embracing: the point of view of an angel, perhaps. But the film never tries to escape reality. Rather, it poses a question: however terrible this world may seem, why would anyone want to escape it?