As tales about the dark side of humanity go, moviegoers would be hard-pressed to find a film more disturbing than “Killer Joe.”

Sex, greed, betrayal, and murder are all on full display in this grand tale of immorality from director William Friedkin -- the filmmaker who rattled the world in 1973 with “The Exorcist.”

Yet as violent and brutal as “Killer Joe” is, Friedkin’s cynical tale about a down-and-out drug dealer who hires an assassin to kill his mother is powerful to watch thanks to the performance of its actors and is likely to launch heated debate once it rolls into theatres on Aug. 10.

“A lot of people want ‘E.T.’ when they go to the movies, and that’s fine.  I think Steven Spielberg is a great filmmaker. But that kind of pure escapist entertainment is just not in my nature to do,” said Friedkin.

“I’ve always been an intense guy, and I want my audiences to feel like they have had an intense experience when they watch my films,” the 76-year-old director told CTVNews.ca during the 2011 Toronto International Film Festival.

“I might be one of the last guys in Hollywood who wants that. But anything else doesn’t much interest me,” he said.

Based on the 1993 play written by Tracy Letts, “Killer Joe” stars Matthew McConaughey as the film’s sleazy, sheriff-cum-hit man, Joe Cooper.

“Into the Wild’s” Emile Hirsch co-stars as Chris Smith, the trailer-park criminal who enlists Joe’s services.

Crippled by debt, Chris hires Joe to dispose of his mother and collect the insurance money. The congenial contract killer is happy to comply. However, because of the complexity of this job, Joe demands advance payment.

With no other options, Chris agrees to give his sister Dottie to Joe as a sexual retainer until the insurance money comes through.

“It’s an evil twist on the Cinderella story,” said Friedkin.

“Lot of little girls dream of being swept off their feet by Prince Charming. Joe is dangerous and capable of doing anything. But he becomes Dottie’s Prince Charming. He just happens to a hired killer,” he said.

British actress Juno Temple, 23, delivers a standout performance as Joe’s teenaged bedmate.

Last seen in “The Dark Knight Rises,” Temple landed the role after sending an unsolicited audition video to Friedkin in which she read some of the script with her 10-year-old brother.

“I had no idea who Juno was,” Friedkin said. “I was going to go with one of three well-known actresses.  But when that tape came in I knew I’d found Dottie,” he said.

Friedkin postponed the film’s start until Temple turned 21 in 2011.

“It was the right thing to do, particularly because of the sexual scenes Juno had to do with Matthew,” said Friedkin.

Some moments are genuinely creepy, particularly when Joe surveys Dottie’s young body. But Friedkin stands by his film.

“There are moments here that get under your skin, just because what transpires between Joe and Dottie is so wrong. But that’s life. Bad things happen all the time,” said Friedkin.

McConaughey, 42, also shines and is anything but a romcom dreamboat in his role in this film.

“Matthew is a really good-looking guy. But that can be a blessing and a curse,” said Friedkin.

“To my mind Matthew had the chops to make Joe seductive and deadly. He can do a lot more than show up, take his shirt off and get a woman into bed,” he said.

Born in Chicago in 1935, Friedkin first found fame with the release of “The French Connection” in 1971.

Shot in a gritty, documentary style that was new for Hollywood features, this story about thugs smuggling drugs between Marseilles and New York City won five Academy Awards, including an Oscar for Best Picture and Best Director.

Friedkin followed that success with “The Exorcist,” the wildly successful horror film based on William Peter Blatty’s best-selling novel.

“The Exorcist” grossed more than US$441 million worldwide, making it one of the highest-earning movies of all time. It also earned 10 Academy Award nominations, losing Best Picture to “The Sting.”

Friedkin went on to direct “To Live and Die in L.A.,” “Rules of Engagement,” as well as the 2006 horror film “Bug,” which causes a sensation at the Cannes Film Festival because of the raw, shattering and critically-acclaimed performances given by Ashley Judd and Michael Shannon.

But one constant is that Friedkin’s work revolves around the dark side of humanity.

“When you have lived as long as I have you learn that good and bad can come in the same package,” said Friedkin.

“We humans can be the best and the worst creations on the planet. We can do marvelous, inspirational things and we can kill. That reality will always grab me,” he said.