PARK CITY, Utah -- A funny thing happened to Colin Farrell on the way to the Dr. Phil intervention.

After becoming as notorious for his off-screen antics -- the four-month marriage, the sex tape, the carousing -- as for his erratic, high-profile film work, he suddenly rehabbed, laid low and retrenched.

The result? A wrenching, hilarious career-best turn as a soul-sickened hitman in the fierce, foul-mouthed crime comedy In Bruges. Phil McGraw, you may not be needed, after all.

In Bruges opened the Sundance Film Festival Thursday night and yesterday the reformed bad boy, stubbled and sleep-deprived, sat down for a post-premiere news conference. (Still, some habits are harder to kick than others: As Farrell takes a seat, he turns grimly to director Martin McDonagh, telling him, "They forgot the ashtray.")

In Bruges, inspired by a vacation award-winning playwright McDonagh once took to the film's namesake, stars Farrell and Brendan Gleeson as contract killers sent into hiding in Belgium after botching a London hit. For the 31-year-old Farrell, it will likely be seen as a turning point: A shift from tabloid target to respectable actor. If that's the case, it's long overdue for someone who, after almost a decade in the spotlight, confesses to feeling uneasy with his own fame.

"You know, man, I never really thought I was in bed with my celebrity or even had a particular understanding of it," he tells Sun Media following the news conference. "The whole concept of celebrity is still something that remains elusive to me. There were a few footballers I loved when I was a kid and I had autographs. I remember the futility of looking at these pieces of paper and going, 'Well, what the f--k do I do with those signatures now?' "

The topic of celebrity, though, is an apt one at Sundance, which has grown into an intersection of commerciality and creativity. Despite receiving the sought-after opening slot at Sundance, In Bruges will likely remain a tough sell for mainstream audiences. It's rude and bloody and profane. And did we mention funny? Again, this is new terrain for Farrell, best recognized from Miami Vice and Phone Booth.

"I know I'm not known for having a funny bone in my body and I've mostly done dramatic pieces for the seven years to varying degrees of success or failure, however you look at it," he says.

"This was an incredibly funny script to read, but the pain that's inherently there, from the perspective of my character, was never that far below the surface. It was always bubbling."

As are elements some viewers, like the saying goes, may find offensive. Namely, that the lead character, worse than being a murderer, is also an unrepentant bigot. "There may be fingers pointed and all that good stuff," Farrell says of the reaction the film could receive when it opens wide next month. For now, he's just pleased it got the chance first to be screened in Park City.

"My understanding ... is that Sundance is a festival about absolute freedom of expression, if nothing else. And political correctness and freedom of expression don't really live within the same realm. Political correctness is something you have to be very careful with -- there's a certain amount of denial there. It can be counter-productive."

Says Gleeson, "For all the cruelty and carnage ... you never, ever hate any of those characters because there's a humanity about them."

And all involved appear buoyed by the positive response In Bruges received at its premiere.

"I had never experienced such a tangible reaction. It was nice," Farrell says. "Good food for the soul and all that s--t."