Sex, sensuality and the rocky relationship between Sigmund Freud and Carl Jung take moviegoers on quite a trip in the new period drama, "A Dangerous Method."

Set in Vienna on the eve of the First World War, Cronenberg digs into the turbulent, six-year friendship between 29-year-old psychiatrist Jung (Michael Fassbender) and his famous mentor Freud (Viggo Mortensen).

"Freud and Jung are always talked about as the fathers of modern-day psychiatry. But they aren't rarefied giants here. They're men with flaws, just like the rest of us," says Cronenberg as we sit and chat by a sun-streamed window in the Intercontinental Toronto Centre.

In Cronenberg's film, the wry father-figure Freud (shown as a man of 50) is jealous of Jung's youth and money, while the earnest Jung dares to challenge Freud's ideas.

Jung also breaks the cardinal rule between doctor and patient. He sleeps with a troubled woman in his care and the sex scenes portrayed in "A Dangerous Method" are masochistic.

The woman is Sabina Spielrein, a real-life patient of Jung's, played in the film by Keira Knightley. When the movie opens, she's dragged screaming into a Zurich clinic and put into Jung's care.

"Keira and I talked a lot about what pitch we should take here, which some people may find extreme. Keira had to express the real horror of hysteria, something doctors back then called a female disease. But that diagnosis had a lot to do with the culture of the time and the repression of women and their sexuality," he says.

"We toned it down a lot. If people knew anything at all about Sabina's story and what transpired between her and Jung they'd see that the pitch here isn't extreme at all. It's actually quite restrained."

Adapted by Christopher Hampton from his stage play "The Talking Cure" (the term for the early development of psychoanalysis), the film takes a smart, dialogue-heavy route through complicated subject matter.

"You do a film and you hope for the best," Cronenberg says calmly.

Yet that calm seems remarkable given the obstacles the 68-year-old director faced on the project.

Christoph Waltz, Cronenberg's original casting choice for Freud, campaigned hard to win the part. When the bigger-budgeted film "Water for Elephants" came along, Waltz emailed Cronenberg to pull out.

Before that, scheduling conflicts forced Christian Bale to withdraw from the role of Jung -- a turn of events Bale personally conveyed to the director.

Cronenberg's hunt for financing also came at a time when the world markets crashed.

"It wasn't pretty. But it really didn't worry me," Cronenberg says, his blue eyes crinkling from the sunlight.

"If you've been in this business for as long as I have, you learn. Things go up. They go down. You just go on."