Babel (15) <!-- none onestar twostar threestar fourstar fivestar -->

"Only connect," wrote EM Forster, this being the principle and pivot on which the Mexican-born director Alejandro Gonzalez Inarritu has founded all three of his films hitherto. Each has leapfrogged its predecessor in ambition and scale. Amores perros (2000) confined itself to a city as it examined the repercussions of a car accident; 21 Grams (2003) also built a multi-story with a terrible accident as its keystone, and this time the setting was a country.

Now, in Babel, Inarritu has opened the frame wider still to encompass three continents, several families and a barrelful of tragic misadventures. Our choices, our actions, can have wildly unforeseen consequences, says the film; if you were to kill yourself after seeing it (it's probably depressing enough), be assured that your suicide will eventually have a momentous effect upon some Inuit tribesman, Finnish loss-adjuster or Korean watch-mender. Welcome to the global misery-go-round.

Inarritu, working with his regular associate, the screenwriter Guillermo Arriaga, combines the artful with the arbitrary; like a compass with a dodgy needle, it's never quite clear which direction he's taking us in.

Babel begins with the story of a Moroccan guide schlepping over the mountains to sell a hunting rifle to his friend, a goatherd. The goatherd then hands the gun to his two teenage sons, telling them to go shoot jackals. Instead, they practise their marksmanship on a tourist coach on the road below, and an American woman (Cate Blanchett) is gravely wounded; her husband (Brad Pitt) spends the rest of the story frantically trying to get her to a hospital.

He also phones home, San Diego, to ask his housekeeper (Adriana Barraza) to look after their two young kids. She promptly takes them across the border to her son's wedding in Mexico - with unhappy results. Meanwhile, a deaf-mute Japanese schoolgirl, Chieko (Rinko Kikuchi) is grieving the death of her mother and cold-shouldering her father (Koji Yakusho), whom she seems to blame. When sorrows come, they come not single spies...

At one level the film is compelling, because Inarritu has such assured command of his camera; he transfixes you with his attentiveness. Watching it becomes a kind of sensory experience; we know, or can guess, what it's like to smoke hashish from the pipe of a wizened crone in Morocco; what it might be like to wander, utterly lost, through a desert at night; or, in the most stunning sequence, to join Chieko in the Bacchanalian excitement of a Tokyo club as a single repeated riff (it's the intro to Earth, Wind and Fire's disco stompalong "September") suddenly cuts to silence, and then to know what it's like to be deaf. Terrifying, in a word, because Chieko can feel the monstrous beat of the music without the emollient effect of the melody.

The film, crisscrossing borders, suggests that language divides and estranges people, but at least some people have ears to hear it with. There is no language sadder than sign language, for it measures out a chasm of isolation even from one's own kind: the girl's longing to be touched, which prompts her into unseemly behaviour (kissing her dentist), becomes almost too poignant to bear.

You could say the same for the Mexican help, who has faithfully minded the children of her rich white employers and is then punished for it. And for that Moroccan goatherd, whose fatal leasing of the rifle comes of stupidity, not malice. Inarritu, film-maker as recording angel, picks up these signals of distress and fashions them into startling, sometimes horrifying, scenes - if you ever wondered what it's like to watch the emergency stitching of a wound, without anaesthetic, here's your opportunity.

But do these scenes really add up to something profound? The burden of the film seems to be that suffering is permanent, universal and quite often the direct consequence of being in a family: parents fail their children, or an errant nephew (Gael Garcia Bernal) betrays his aunt.

As a mosaic, however, the pieces don't really fit together, beyond the arbitrary design imposed by the script. We discover how that rifle ended up in the hands of the mountain guide - it isn't sinister, just a random act of generosity that teaches us nothing. There is no rhyme or reason to these tragedies, and there are no consonances in the story that suggest how things could be different. If only we could all... what? Be kinder, possibly, though that is not a benefit the Mexican mother or the Moroccan father is awarded.

Inarritu and Arriaga, terrific with individual scenes, have so little interest in pattern or coherence that their film sometimes feels like wanton misery-mongering, and the performances are geared accordingly. Brad Pitt, greying and bearded, is unusually persuasive; if he'd bulked out he might have been in the running for an Oscar. Adriana Barraza is magnificent as the suffering madre, and Rinko Kikuchi as the deaf-mute schoolgirl etches a portrait of loneliness so raw you want to look away, but can't.

Babel pulses with sound and fury - Gustavo Santaolalla's score melds the disparate influences wonderfully - and confirms Inarritu as one of the most exhilarating of film-makers. If it had as much meaning as it pretends to, it would be a masterpiece.