If ever there was a film aptly named it has to be Filth, director Jon S. Baird's adaptation of the novel by Irving Welsh.

The film starts with Bruce Robinson (James McAvoy, Trance, X-Men: First Class), a Scottish cop who is keen to climb up the ladder of success and gain promotion; in doing so, he believes he will win back his wife's affections after a recent separation. So when he is given the chance to front up a recent murder inquiry, Robinson sees this as his chance and he intends to take it even if it means discrediting those around him. The problem is that the bigoted Robinson has secrets; he's dependent on alcohol and drugs, and that, coupled with the fact he's bipolar makes him one messed up individual. So what at first glance what seems like a story of success is in fact a complete role reversal, the one question the audience is left with though is how low he will go.

Robinson gets his kicks out of playing one fellow cop off against another, unnerving them, and manipulating them for his own selfish needs. Sleeping around with work colleagues or their wives means nothing to him, it's all part of the game—his game, his rules. At his lowest moments, imaginary physiologist Dr Rossi (Jim Broadbent, Cloud Atlas, Hot Fuzz) appears in his head, as if trying to veer him onto a more righteous road. It's almost a haunting, a trigger for the orgy of drugs, sex and drink to start all over again. At one point he says "There's something seriously wrong with me"; I was left wondering how much more can this man take.

As dark as the film is, the humour certainly lifts the mood in the first two thirds—there are some great one liners in there—but there comes a point when the laughing stops and the pity starts, as McAvoy's skill as an actor grips you. There is no doubting that McAvoy has talent, his role of Simon in Trance is one of my favourites of the year so far, but his performance as Bruce Robinson well and truly exceeds that. Seeing McAvoy's Robinson become more isolated and withdrawn kind of hits you without you knowing it. The furore of his curt manner in front of others, changing to the despair while he is on his own, all the while his eyes, sunken, telling the true story.

Writer/Director Jon S. Baird keeps Filth moving well, pacey enough to keep your interest, always drip-feeding you little by little the depravity a human being could descend to. Helped by a great supporting cast and soundtrack to boot, it is of no surprise that there are many comparisons being made between this and the 90's classic Trainspotting, Danny Boyle's adaptation of an Irving Welsh novel, and Filth is up there with it. The litmus test will be if it is judged in cult status, as Trainspotting is today, fifteen years from now.

So the bottom line, is Filth worth seeing? Definitely; Baird has managed to make a thriller that gets darker the further in you go, tinctured with some outrageous humour. But be warned—throughout there is sex, drink and drug use, homophobic remarks and foul language that will make those who lobby for political correctness spit nails, and if you are the type that is easily offended it may not be to your liking.