David Cronenberg's A Dangerous Method explores the early days of psychoanalysis, so it was perhaps fitting that the stars schemed to drive the Toronto-born director crazy in his own backyard.

Keira Knightley and co-star Viggo Mortensen sported Montreal Canadiens hockey jerseys at the start of the film's Toronto International Film Festival press conference on Saturday, much to the chagrin of Cronenberg.

“He [Mortensen] told me it would wind David up, so we decided it would be a good idea,” Knightley said, admitting she had no idea of the significance of the sweaters.

Expressing mock dismay, Cronenberg quipped that their stunt — performed in the hometown of the Toronto Maple Leafs — was "perverse."

Keira Knightley and Viggo Mortensen hoist a Montreal Canadiens jersey on Saturday, much to the displeasure of the Toronto-born director of A Dangerous Method, David Cronenberg. Associated Press

Set in Vienna in the early 1900s, A Dangerous Method touches on the complex relationship between novice psychoanalyst Carl Jung (Michael Fassbender) and his mentor Sigmund Freud (Mortensen).

Studying the methods of Freud, Jung also develops his own theories based on the clinical study of psychologically disturbed patients. But when an educated but sick young Russian woman arrives at the clinic, he becomes fascinated by her case and spellbound by her dangerous sexuality. Sabina Spielrein (Knightley) stirs unconscious emotions within Jung, as he begins to probe her dark past.

Knightley said playing the part of a mentally disturbed, but complex woman was a difficult task.

“It was a very challenging role and I think that was one of the reasons why I really wanted to play her because I really didn’t know who she was,” the British actress told reporters in Toronto.

“It really was a question of trying to find logic within what was perceived from the outside to be madness. As much as she knew that she was ill, there were logical reasons for the way in which she behaved.”

Spielrein, who later became an analyst herself, was also a character that fascinated screenwriter Chris Hampton.

“One of the things I really wanted to do was to bring her back into prominence. She was a remarkable woman who had an exemplary career and actually had a lot of input into the ideas of both the men,” he said.

Though this latest role sees Knightley play a mentally disturbed woman, the actress said she has no plans to visit a psychiatrist any time soon. Instead, the star of Never Let Me Go, Pride and Prejudice, Atonement and two Pirates of the Caribbean movies will depend on her craft to keep her sane.

“Acting is what keeps me grounded. Acting is therapy…I think it is incredibly cathartic and particularly playing a role like this. It is almost strange what a wonderful time we had,” she said.