London River (12A)

Powerful acting recalls the aftermath of the 7/7 attacks.

London River (12A)
dir: Rachid Bouchareb

Under normal circumstances, I would advocate harsh punishment for the makers of any film that takes more than a passing interest in London's red double-decker buses. Force these hacks to spend a sticky summer's day on one, or make them struggle upstairs to the top deck just as the vehicle is lurching away from the kerb - nothing's too cruel for 'em.

Rachid Bouchareb, the French-Algerian director who made Days of Glory, has special exemption. Cliché is overruled instantly by the context of his new film, London River, which is set during the weeks following the suicide bombings of 7 July 2005. Whenever the camera zeroes in on a double-decker bus, it sees not a tourist-friendly emblem, but a vessel of incalculable danger.

The first bus on screen is the number 30, standing in Tavistock Square like a gaudy present ripped open by an impatient child. Elisabeth (Brenda Blethyn), a widowed churchgoer, is watching the TV images at her home in Guernsey. She calls her daughter Jane, who lives in Finsbury Park, partly because she wants to know she's fine, but also to share in the horror. There's no reply.

Knowing as we do that her calls will continue to go unanswered doesn't diminish the anguish of those early scenes. Anyone who has felt anger kick in to anaesthetise the panic when your child has wandered off in a supermarket will recognise Elisabeth's mounting irritation as the voicemail messages pile up. Blethyn is a beautifully transparent performer. Here, as with her work in Mike Leigh's Grown-Ups and Secrets and Lies, you can see her thought processes. She lets you hear the penny drop.

Eventually, Elisabeth comes to London. The police, unable to help, suggest she check the casualty lists at hospitals. Ousmane (Sotigui Kouyaté), an African Muslim searching for his son Ali, receives the same advice. Where Elisabeth is short, twitchy and suspicious, Ousmane is regal, serene and taller than the Post Office Tower. His stiff black beard is flecked with silver, like frost on coal; he carries a briefcase that looks as small as an envelope in his hand. He walks with a stick, slowly and purposefully, as though setting down his footprints for all eternity.

For a while, Elisabeth shuns him, and he lopes behind her like a shadow. Gradually, it transpires that Jane and Ali knew one another. If that's too contrived, which it probably is, the film can still subvert our expectations. There's the rough-and-ready police officer who declares an unusual allegiance and the candid heart-to-hearts in which Elisabeth expresses her suspicions about Ali, only to hear them echoed by Ousmane. Armand Amar's score, with its lonesome saxophone and antsy percussion, also catches you out. It could be on loan from a smoky, late-night noir, but it fits this outsider's view of a city subdued.

Like Tom McCarthy's The Visitor, London River captures the buzz of post-attack paranoia as well as the connections forged by disparate people in crisis. While the screenplay calls upon Elisabeth to tell Ousmane that their lives are not so different, imploring messages of religious tolerance are mostly left implicit. Where the film becomes problematic is in the tension between the search for missing relatives and the hope of finding them. When the possibility arises that Jane and Ali may not even have been travelling on the morning of the bombings, we are faced briefly with the prospect of a film about 7/7 in which none of the main characters experiences any lasting loss. A version of London River featuring Jane and Ali turning up in sombreros and ponchos, having skipped town for a holiday, would be in bad faith. It's not pleasant to admit, but we need the pain that the film has promised in its pact with us.

It comes, quietly, in a pair of telephone conversations. In one, Ousmane makes a matter-of-fact call to Ali's mother, reporting on his progress. In the other, Elisabeth leaves a message for Jane after discovering details of her daughter's love life. "Does this mean I'm going to have to buy a new hat?" she trills, trying to will an alternative future into existence by sheer emotional force.