The Legend of Barney Thomson is the directorial debut of actor Robert Carlyle, and it’s one of those black comedies about a serial killer in which, as the bodies pile up, plausibility edges closer and closer to the window until it flies out completely. (No. Wait. Come back! I’ll massage your feet!) This wouldn’t, in fact, matter at all if there were something else to hang onto; if the characters were involving, or the story was told with wit, zip and panache, but it just monotonously drones on. The central figure is a barber so I guess you could say this is Sweeney Plod rather than, you know, that other one.

Set in Glasgow, and based on Douglas Lindsay’s comic crime novel The Long Midnight of Barney Thomson, Carlyle stars as Barney; Barney the barber, who lives a life of desperate mediocrity — he says so himself in one of those first-person voice-overs — and who has suffered demotion after demotion at work. You have no chat, no banter, you hang over clients like ‘a haunted tree’, his boss complains and, to be fair, his boss has a point, as this Barney has no charm whatsoever, and if you wouldn’t wish to get your hair cut by him, why you would wish to buy a cinema ticket and spend 96 minutes in his company is anyone’s guess. Eventually, his boss fires him, at which point Barney accidentally kills him with a pair of scissors. Oops. But at least there is no blood to mop up. Clean as a whistle that barbershop floor, after the event. This is when plausibility first starts edging towards the window. (No! Wait! I’ll be your slave for a week!)

Matters get yet more complicated, as a serial killer is on the loose; a killer who sends his victims’ body parts back to loved ones in the post. (The film opens with a severed penis in a box, which may actually be the best place for a penis, once severed.) The cop heading the investigation into these murders is Ray Winstone as Inspector Holdall. Holdall, who is English, drips bitter hatred for his own position in life, and for having been posted to Glasgow, and is described as ‘a big slab o’bastard’, so Winstone isn’t exactly stretched, shall we say. He pursues Barney, thinking he’s the serial killer, while scrapping over the case with an hysterical rival cop, as played by an hysterical Ashley Jenson. (That is, hysterical in the true sense, rather than the funny sense; nothing here is hysterical in that way.)

As Barney bunglingly attempts to get rid of his boss’s body, and haplessly racks up another (bloodless) murder, comedy is sought but it is never, alas, properly found. The sight gags — see penis in box, above — are childishly tiresome, while the foremost comedy character is, I think, meant to be Barney’s mother. This is Cemolina, as gamely played by Emma Thompson performing against type. Cemolina wears a faux ocelot coat which, in film, is always shorthand for: common. Cemolina goes to the dog track and to bingo and smokes and drinks and swears and is as unmotherly as she is plain nasty. I don’t know. Is this funny? The film certainly invites us to sneer at her, but in a way that feels deeply unpleasant somehow.

I’ve no idea what Carlyle set out to do exactly, or even if he had any idea what he was setting out to do, while setting out to do it. My impression is that he didn’t. The film doesn’t even own a particular style. Instead, it’s a little bit Coen brothers and a little bit Filth and a little bit Trainspotting and quite a bit Reservoir Dogs, particularly in its risible resolution, by which time plausibility has said its goodbyes and is long gone.

Also, when is this set? It seems like the 1950s, mostly. Everything is shot through a dusty miasma. The barber shop is one of those old-fashioned ones with several staff, all wearing burgundy nylon jackets. There are no mobile phones. The soundtrack is retro. But then suddenly, there’ll be a mention of Brad and Angelina, or you’ll spot a Kasabian poster on a wall, and all the cars on the road, they are the cars of today. It’s distracting and confusing as well as, frankly, seriously weird. Sweeney Odd? Yes, I guess you could say it is that too.