The unimpeachable talents of Ewan McGregor, Tilda Swinton, Peter Mullan and Emily Mortimer go for naught in "Young Adam," a film of dark, disenchanting characters who tread water in moral ambiguity for 98 minutes.

McGregor plays Joe, a nebulous, failed beatnik writer who has deliberately dropped off the face of the earth by taking a grimy, hard-labor job, working (and living) on a cramped little coal barge that travels the shallow, narrow backwater canals of 1950s Glasgow. Vacant of disposition and void of moral fiber, he's become both a reluctant drinking buddy to his boss Les (Mullan, "Session 9") and an opportunistic lover to the boss's weary, vinegary wife Ella (Swinton, "The Deep End"), which soon upends all their lives.

Proving he hasn't abandoned his provocative sensibilities to Hollywood, McGregor makes Joe's soulless impalpability curiously absorbing in a performance full of furtive nuance and vague instability -- the signs of which grow as he finds a young woman's dead body in the water and director David Mackenzie slowly reveals that his protagonist may have had something to do with how she got there in the first place.

In several chronologically muddled flashbacks, Joe's previous life as the volatile, sexually abusive live-in boyfriend of the same girl (Mortimer, "Lovely and Amazing") is revealed, as are more recent encounters in which he runs into her on the street and seduces her on the waterfront, leading to a bleak, highly unlikely sex scene on the muddy pavement beneath a lorry.

No matter how low her self-esteem, I don't buy that any girl would acquiesce to this. But apparently Joe is supposed to be catnip to unstable women in proletarian Scotland. Every female with a speaking role in "Young Adam" sleeps with the guy (often within hours of meeting him) even through he's is a dreary, mundane cuss made interesting to the viewer only because we have a vague insight into his unsound psyche.

Much of that insight comes from the curiosity and negligible pangs of guilt that arise in him when the girl's more recent lover -- a married plumber -- is charged with her murder. But over the course of the story, even attending the trial has no significant impact on Joe, the practical upshot of which is that his character doesn't develop in any discernable way.

Adapted by Mackenzie from the inexplicably titled novel by Alexander Trocchi (himself an unhinged Scottish beat writer), "Young Adam" may have intensity (thanks to its capable cast), grit and turbulent sexuality (the film received an undeserved NC-17), but it seems to go nowhere emotionally or even allegorically. Not one character evolves over the course of the film, so powerful performances or not, what's the point?