Ex Drummer, the debut film from Koen Mortimer, leaves you feeling invigorated and disgusted --as if you'd just taken a shower in a high-pressure blast of hot sewage. Ex Drummer takes one of the oldest standby rock film plots -- the battle of the bands -- and sends it on down a road to hell paved with bleak absurdity and grim energy. It's hard to watch. It's even harder to stop watching.

Our hero -- but he isn't -- is Dries (Dries Vanhegen), a successful novelist who lives in one of those Fortress of Solitude-looking high-end apartments where he can look down on the city that made him. One day three musicians come to call -- they're looking for a drummer. There's a music festival coming up they want to play, and win. They figure having a famous novelist on the traps might help with their novelty value. Their gimmick? They all have handicaps. Dries's handicap? He can't play the drums. Mortimer's film is adapted from a novel by Flemish author Herman Brusselmans, but the filmed version is an assault on your senses -- the clamor and squalor of every scene, the physical and moral rot so strong you can almost smell it coming off the screen.

Oscar Wilde said we are all in the gutter, but some of us are looking at the stars. Dries isn't looking at the stars: he's looking at the drain, wondering just how far down it goes. ... The band (dubbed The Feminists for extra shock value) includes a bassist with a stiff arm, a deaf guitarist and a lead singer with a taste for aggravated sexual assault. It's not Dries's usual crowd. That makes it all the more appealing to him. He's using the band. The band's using him. This can't possibly end well.

And it doesn't, in a spectacularly unexpected fashion that takes the relationship between Dries and the band from mere opportunism to something far darker. Along the way, Mortier pulls every cinematic trick in the book and then some to show the fractured, flailing, messy relationship the band and Dries -- from upside-down sets to reverse-film sequences to what may be the single most vulgar piece of set design ever made for the purpose of what's essentially a very large, very smutty dick joke. I was appalled. And amused. And appalled again.

Vanhegen's performance is a mini-masterpiece of screw-you cool -- he's magnetic and repellent, ruling through contempt -- and he throws heart and soul into playing a heartless, soulless bastard. Toronto International Film Festival program chief Colin Geddes compares Ex Drummer to Trainspotting, but Danny Boyle's story of the smacked-out Scottish underclass had a weird sort of optimism to it; no such relief is in sight here, and maybe it shouldn't be. Ex Drummer takes place in the Id-fueled undermind of rock, where young men scream their inarticulate rage through microphones and amplifiers in a futile hope they can shout it silent. They don't; they can't. As the bloody, bleak finale unfolds, you're terrified and exhilarated in equal measure. Ex Drummer's a short, sharp shock of bleak black comedy -- and that's in no small part because, yes, the joke's on you, too.

(Ex Drummer plays Sunday, September 9th at 12 pm at the Toronto International Film Festival.)