In This World (15)

Michael Winterbottom's recent run of pictures has been distinguished by a vivid and uncommon feel for the significance of place. Nothing in his career so far has been an out-and-out success, his work too often let down by errancies of tone and plotting, but as regards the specific moods of location he's definitely got something. It first became apparent in Welcome to Sarajevo (1996), not a city difficult to find drama in but nonetheless finely rendered in its chaos and carnage.

There followed an intense, neurotic vision of Hastings in I Want You (1998), the English seaside resort as a Gothic hall of shades; and Wonderland (1999) presented a scruffy, angular London that might have been on a different planet from Notting Hill. Most ambitious of all was the bleak majesty of a Sierra Nevada mining town in The Claim (2001), the dazzling white snowscapes as stark and unyielding as the plot it borrowed from Thomas Hardy's The Mayor of Casterbridge.

His new film, In This World, continues his preoccupation with place, covering two continents in its poignant tale of migrants. Inspired by the brouhaha over immigration during the last election, Winterbottom chooses to focus not on the political rights of asylum-seekers but on the larger human right to a better life. In the current climate the implications will be about as welcome to the Government as a dinner invitation from the French embassy.

Although it has the gritty look of a documentary, with a voiceover intoning statistics about the refugee camp in Peshawar on the Pakistan-Afghanistan border, the film is actually a drama. It concerns an arduous journey undertaken by two Afghans, a 15-year-old orphan, Jamal (Jamal Udin Torabi) and his older cousin Enayat (Enayatullah), who want to start a new life in London.

This is not an odyssey for the faint-hearted, and the travel arrangements are decidedly not of the Thomas Cook school. Even before they hit the road great wads of banknotes are handed over to various fixers and forgers who will provide them with the basic camouflage of migration.

The screenwriter, Tony Grisoni, doesn't supply us with much back story on Jamal and Enayat, nor do we discover exactly why they choose London as their ultimate destination. What's clear is the desperate, impoverished surroundings they have lived in (the camp was established in the wake of invasion by the Soviets in 1979) and their determination to leave that world behind them. Vast expanses of desert stretch out before them as they journey through Quetta and Tehran, braving sandstorms and border patrols; Jamal, the shrewder of the two, knows that survival comes at a price, and gifting a Walkman to an inquisitive official will save them trouble in the long run.

The shaky digital video lends the film an immediacy and emotional directness quite different from Winterbottom's previous work – its austere use of technology could practically qualify it as a Dogme film. The more time we spend with the two travellers, the fonder we grow of them. Jamal loves to spin yarns, and tries to teach Enayat a little English during lulls in the journey.

Orson Welles once said that there are only two kinds of emotion on a plane: boredom and terror. Imagine them intensified over days of living rough in trucks, buses, dosshouses, crouched beneath crates of fruit or stamping over hills in sub-zero temperatures while armed soldiers roam nearby. As the terrain becomes more civilised and populous, so does the danger increase: work in an Istanbul sweatshop comes to seem a blessed relief compared with what they must endure on a freight container to Trieste. (The sequence recalls the horrific news report of people-smuggling in June 2000 when 58 Chinese immigrants were found dead in a lorry that passed through UK Customs.)

The film's effect is cumulative, in the manner of recent Iranian cinema such as Blackboards and The Circle. Images rather than dialogue are its currency. One of its most telling moments is on the shore outside Sangatte refugee camp, where the film crew were refused entry. While others play football on the sand Jamal looks out to the Channel as a ferry sails over the horizon; the sudden longing of a child for escape is vividly imprinted.

In This World could also make a companion piece to Stephen Frears's Dirty Pretty Things, a portrait of dislocation and exile that picks up the story where this film ends. Both make us look again at the people we glimpse out the corner of an eye – here, the pestering street kid selling gewgaws, as Jamal becomes – and invite us to ponder their fate once we blank them.

Yet the film, for all its passion, doesn't hammer its moral points. It is at heart a road movie, and its nonjudgmental tone feels more likely to win it friends than an overtly political tract would. The sting in its tale is that Jamal, who is an actual refugee now living in London, will have to return to Peshawar the day before his 18th birthday. Reality has just blown a hole through the scrim of fiction, and our final sight of him, his head bowed, whispering a prayer, is deeply affecting. In This World probably doesn't stand much chance of reaching a wide audience, but it does enormous credit to Michael Winterbottom and his team. It also puts him in a different league as a film-maker.