You have to hand it to James McAvoy, who has made a career out of his amiable, boyish good looks; in Filth, he destroys that image. As Detective Sergeant Bruce Robertson, he's a booze-bloated, greasy wreck who appears about 20 years older, all busted capillaries and shit-eating grin. He's not unrecognizable so much as suddenly repugnant, and seeing traces of the clean-cut star in this self-destructive shell of a man makes his character even more disturbing.
Robertson is a drug-addicted sociopath who screws, and screws with, anyone within firing distance. Ostensibly, he's bent on ensnaring a promotion, which his superior is dangling like a cat toy in front of his department — Robertson's glamorous wife (Shauna Macdonald) explains in cooing voiceover that it's she, "the ultimate tease," who demands this advancement. But aside from the lusty fantasy he associates with the promotion, Robertson hardly cares about his job at all; he prefers to stoke internecine conflict and revel in the resulting chaos. When called into a dingy meeting room to discuss a newly opened murder case, Robertson's first order of business is to let out an impish fart. Let the games begin.
After high jinks and a few sexual assaults, it becomes clear that the promotion is merely a MacGuffin to keep things moving as Robertson's personal life collapses. Aside from familial problems, Robertson is plagued by vague guilt over his brother's death as a child; there's also a heavy-handed subplot connecting him to a recent widow (Downton Abbey's Joanne Froggatt). These melodramatic details read like attempts to justify Robertson's appallingly bad personality, and such sincerity doesn't jibe well with director Jon S. Baird's slick style, which involves lots of slow motion, skewed POV shots, and pointed looks into the camera. The insistent claim that Robertson is a troubled but essentially sympathetic person seems as nonsensical as the leering animal masks that start popping up in the film's final third.
Baird does much better when wrangling an entertaining assortment of supporting players, including Jamie Bell and Imogen Poots, who help paint Edinburgh as a circus-like dystopia populated by cartoonish egomaniacs. One well-meaning foil appears in the form of Robertson's unfortunate best friend, Bladesey, played by the excellent character actor Eddie Marsan. Robertson subjects the oblivious Bladesey to various abuses, harassing his wife (Shirley Henderson) and dosing him with ecstasy on a weekend stag trip. Finally, Bladesey asks, quite reasonably: "Why do you bully me, Bruce?" This is the first time someone has questioned his nature so straightforwardly; naturally, Robertson ends the conversation by punching his friend in the face.
Filth is adapted from a novel by Irvine Welsh, who also wrote Trainspotting (a fact proudly advertised in Filth's trailer). Welsh isn't the only link between the two films — Baird recently collaborated with Trainspotting director Danny Boyle on the British television series Babylon, and McAvoy also starred in Boyle's Trance. But comparing Filth to that earlier work only illuminates its shortcomings. A self-aware sociopath is a tough character to humanize, especially when he's mired in a stylized jumble of comedy and tragedy. A bizarre twist (would it be too much to ask for this film not to bang us over the head with a twist?) tacked onto the end kills any remaining momentum, and Filth ends up wheezing across the finish line, dragging a load of kinky juvenilia behind it.