Dir: David Mackenzie. UK, 2003. 93mins.

Scottish director David Mackenzie recently divided British critics with the release of his first feature, the rough-and-ready digital drama The Last Great Wilderness. His follow-up, Young Adam, is a more rigorous proposition that amply confirms Mackenzie's promise. A powerful, disturbing adaptation of the novel by Scottish beat-generation figure Alexander Trocchi, Young Adam is visually distinctive and narratively uncompromising. It will startle devotees of Ewan McGregor's recent matinee-idol persona. McGregor, in arguably his most vivid and complex performance since Trainspotting, will certainly help Young Adam's box-office profile, and no doubt explains the otherwise surprising involvement of Warner Bros as distributor of this unapologetically severe production. But its dark aesthetic and subject matter will limit its mainstream commercial appeal, though it should find a warm welcome on the arthouse circuit and in festivals.

Despite its mystery aspect, the fragmentation and defiant refusal of final resolution will make Young Adam hard to market as a thriller in any conventional sense. This is very much an art film, of the sombre, pensive variety more commonly associated with French directors such as Bruno Dumont. Young Adam would certainly have held its own in a Cannes competition slot, and marks the arrival of a boldly non-conformist voice in British cinema.

The 1950s-set story largely takes place on the River Clyde and the canals between Glasgow and Edinburgh. It begins when Joe (McGregor), a young barge worker, spots a woman's corpse floating in the water and pulls her out with the help of grizzled skipper Les (Mullan). Joe lodges on the barge with Les and his wife Ella (Tilda Swinton), a hard-bitten woman whose dissatisfaction with her husband is only too evident. Joe and Ella begin an affair, literally sleeping together under Les's nose when he is busy above deck.

At first Joe is an enigma - apparently a cynical, taciturn charmer who only seems happy with nose sunk in a Penguin paperback. Gradually, as the narrative unfolds in flashbacks and ellipses, we learn about his frustrated literary aspirations and his fraught, sexually intense relationship with Cathie (Emily Mortimer), a young woman he meets on a beach. The more the audience see of Joe, past and present, the more disturbing he appears: amoral, over-sexed and with a distinctly cruel streak.

In present-day terms, Joe might be regarded as a sociopath; but in this story, which Mackenzie's scene-setting grounds in the literary culture of Trocchi's 1950s, he registers as a classic existential anti-hero with a rootless nature and a dangerous readiness to follow the promptings of chance. His character carries echoes of John Osborne's Jimmy Porter, Camus's Outsider and of the troubled bohemian Trocchi himself.

The story is all the more unsettling in that events seem to unfold with little reference to conventional logic. Joe's affair with Ella initially suggests the familiar triangle of The Postman Never Rings Twice and Ossessione, but Mackenzie artfully defuses the expected tensions: in one memorable long-take scene, the adulterous couple lie in bed calmly wondering whether they have been discovered, but the ensuing confrontation between Joe and Les proves startlingly anti-climactic. Thereafter events follow a dream-like logic, as Joe supplants Les, and Ella's brassy sister moves in, with inevitable results.

The film's numerous sex scenes are exceptionally unvarnished, although collectors of McGregor full frontals are unlikely to complain. But the domestic spat where Joe brutally vents his frustrations on the long-suffering Cathie may be as shocking for McGregor fans as for lovers of custard.

Giles Nuttgens's moody photography, with its simple but often surprising perspectives, makes the river-bound setting an austere, self-enclosed world, the claustrophobia accentuated by the interiors of the barge and tenement apartments. The production design economically creates a dowdy 1950s feel, although some scenes evoke a shabbier world that could easily be the early 1900s. The low-key stylisation does for Trocchi's Scotland what David Cronenberg's Spider did for 1960s London, creating an emotional landscape as much as a realistic one.

The acting is uniformly powerful and subtle, with Swinton especially striking as a woman quietly driven by anger and desperation. Mullan, with softer edges than in recent performances, makes his fatalistic, folk-singing cuckold very sympathetic, while Mortimer is intelligent and sensitive in a highly charged, vulnerable role. While McGregor's well-coiffed dapper appearance may not entirely fit the 1950s scene, his curiously blank charisma works to deceptive effect, keeping us guessing about Joe's personality, which veers unpredictably between charm and outright, uningratiating abjection.

Prod co: Recorded Picture Co, HanWay, Film Council, Scottish Screen, Sveno Media
UK dist: Warner Bros
Int'l sales: HanWay
Prod: Jeremy Thomas
Assoc prods: Peter Watson, Stephen Mallmann, Gillian Berrie
Co-prods: Jim Reeve, Nick O'Hagan, Alexandra Stone
Scr: Mackenzie, based on the novel by Alexander Trocchi
Cinematography: Giles Nuttgens
Ed: Colin Monie
Prod des: Laurence Dorman
Music: David Byrne
Main cast: Ewan McGregor, Tilda Swinton, Peter Mullan, Emily Mortimer, Jack McElhone, Therese Bradley