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 hijinks 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. 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. Filth ends up wheezing across the finish line, dragging a load of kinky juvenilia behind it.