Our era of cell phones, Internet links and globe-spanning travel ought to knock down barriers and bring us closer. Not so, argues Alejandro Gonz á lez I ñá rritu in his complex international tragedy Babel , which tells four heart-rending stories across four countries, in five principal languages.

At the core of each tale is an elemental idea, a family struggling to survive against forces – personal, natural, legal, political – conspiring to pull them apart. Even when we speak the same language, I ñá rritu implies, communication is superficial, mutual comprehension is rare.

American tourists Richard and Susan (Brad Pitt, Cate Blanchett) are traveling in North Africa. They are on a last-ditch mission to reconnect after heartbreak has shattered their marriage. The relationship is as arid as the Moroccan mountains they're exploring. High in those peaks is a herding family whose sparring boys trigger a catastrophe for the tourists and set off an international political crisis.

Watching over Richard and Susan's children in San Diego is their devoted nanny, Amelia (Adrianna Barraza). As she prepares to attend her son's wedding in Mexico, she gets an urgent call from Richard.

There has been a terrible accident; he and Susan will be delayed, and Amelia must look after the children until other arrangements can be made. The servant impulsively decides to take the children across the border for the marriage feast, with assurances from her nephew, Santiago (Gael Garc í a Bernal), that they will never be caught as illegal immigrants.

Linking these stories is a seemingly inconsequential gesture by a Tokyo executive (K ô ji Yakusho). He's a kind and generous man, yet he can't connect with his rebellious deaf-mute teen daughter (Rinko Kikuchi), who has reacted to her mother's recent suicide by acting out.

The girl prowls through nightclubs, hoping to connect sexually with anyone who returns her interest. I ñá rritu drives home her seclusion with silent point-of-view shots, turning the discos into arenas of meaningless flash and frenzy every bit as isolating as the Moroccan desert.

The film is stunningly well-acted, with the director drawing splendid work out of his multilingual cast, even though he couldn't directly communicate with many of them. Pitt and Blanchett are exemplary as the disillusioned Californians, and Kikuchi makes her silent schoolgirl a thunderstorm of unexpressed emotion.

As in I ñá rritu's earlier triumphs Amores Perros and 21 Grams , Babel abounds with puzzling moments, shifts in the time frame and mysteries that fall into place as the tale unfolds. In his world, an act of pure charity can beget consequences that imperil innocent lives, while the tenderness of strangers may be our only shield against imminent death.

The director interweaves his stories like a symphonic composer, teasing out suspense here, adding foreboding there, bringing in a surge of crushing pathos but then providing a blessed note of hope and reconciliation. It pulls off the feat of being at once subtle and clear as day.

Grade: A-