The titular Barney Thomson (Robert Carlyle) is a less than friendly man, he complains about many things and is generally unapproachable. One day he stumbles upon a series of hazardously unfortunate events which lead him into awkward world of crime. This is a very distinct style of comedy, which can be poignantly funny at times, but also riddled with tons of profanity and can be even resentful, thus it probably caters to more adult audience.
Acting is sharply over-the-top as Barney wonders into sillier antics than the last, involving his strange mom as well as detectives hell bent on pursuing a serial killer. It's a harsh unapologetic direction for comedy, a bit similar to Kiss Kiss Bang Bang, certainly not a light watch for casual or younger audience, but for mature demographic the oddities might be a treat.
The cast performs with intense gusto and yelling, which is also one of the movie's quirks. Its accent is very thick, when said in fast pace it can be confusing, so subtitles would be helpful for this case. It can be jarring when the movie tries to pull off a strangely dark tone, borderline uncomfortably so. Furthermore, the actors seem truly invested on delivering all around antagonizing characters, thus there's no real heroes here.
The movie could be vulgar at times, yet its crude and bloody nature might be ironically entertaining.