The trailers for In Bruges, the feature directorial debut from Martin McDonagh, the Britain-born Irish playwright (whose first film, the short Six Shooter, won him an Oscar), make the movie look like more of a errant lark than it actually is. The trailers are not misleading, exactly; yes, the picture is about two hoodlums who are ordered to hide out in the ancient Belgian town of Bruges after a hit gone somehow wrong; yes, the younger hoodlum is a rude hothead who can't stand the staid old place while the older one is more patient and appreciative; yes, the master of the hoodlums goes mondo bonkers after things don't go the way he wants and he's then forced to come after the duo; yes, there is much running, swearing and shooting.

But no, that Pixies song "Something Against You" doesn't play during any of the chase scenes and isn't heard in the movie at all, despite its inclusion in the trailer. The music for the film proper is instead by Carter Burwell, and there's quite a bit of, and it aims for tragic and mournful tones more than hectic and antic ones. This is an important difference. Because for all its very snappy dialogue and daringly crass humor, In Bruges aims to be about, in one character's words, "guilt and sins and hell and all that."

The biggest sin — not a deliberate one, but a big one nonetheless — belongs to Ray, the younger hood, played by Colin Farrell, often in the manner of a vulnerable chimpanzee. I mean that as a compliment. Farrell does lot of acting with his eyes, eyebrows, and jaw line, using his facial muscles as if he's only now just discovered them. And when Farrell inverts his brows, sucks in his cheeks, and sets and resets the lower third of his mug, it's as peculiarly compelling a sight as Anthony Perkins' Norman/Mother trying to get to the correct expression to make everyone believe he's not a fruit loop at the close of Psycho. Farrell's got a great burden to carry, one that becomes greater once the viewer is filled in on just what he's guilty of, but he doesn't falter once. Nor does Brendan Gleeson, playing Ken, Ray's mentor. Gleeson's got an even heavier burden than Farrell in a sense, in that his character type — the soulful older hit man! — is among the easiest to make hackneyed.

Before the fellows tick off their largely lunatic boss Harry — Ralph Fiennes in an oily, fang-bearing, hilariously harrowing performance — to the point where he has to come after them, Ken appreciates the city's ancient beauty and calm while Ray insults tourists, bemoans the lack of anything to do, and stumbles upon a film set, where Ray encounters a fellow he can never decide whether to call a midget or a dwarf or a little person. This diminutive dyspeptic, Jimmy (Jordan Prentice, in a peculiar gloss on Peter Dinklage's role in Living in Oblivion) keeps himself entertained with hookers and drugs, the latter provided by Chloe (Poesy), who Ray comes to see as a kindred spirit. Just how kindred is either called into question or bolstered (depending on your moral barometer) by an encounter with Chloe's quasi-boyfriend, a thug played by an almost-unrecognizable Jeremie Regnier (of L'Enfant, um, fame).

All of these improbable characters entertain, but seem kind of motley…until you work your way backwards from McDonagh's spectacularly fanciful ending, which reveals them all to be cogs in a clockwork mechanism (which recalls, among other things, the denouement of the cult classic The Stunt Man). This finale, which piles one bloody absurd epiphany on top of another almost ad infinitum, is where McDonagh lays all his cards on the table — and his characters are the ones who have to pay up. Viewers might not be entirely convinced that the auteur has actually won the hand. But only the most churlish would not admit that he played a pretty impressive game.