Costume dramas and fairy tales set the tone for the opening days of the 68th Venice Film Festival. David Cronenberg’s hotly awaited “A Dangerous Method,” details the collaboration and rivalry between Carl Jung and Sigmund Freud and set on the eve of World War One.

“A Dangerous Method” arrived on day three of the festival and has been one of the stronger entries in the 22-film-strong main competition program. The Canadian auteur’s latest cinematic foray deals is a bit of change of pace from his previous work. During the press conference Cronenberg even suggested that the film would probably appeal more strongly to fans of Freud and Jung that it would to fans of his remake of “The Fly.”

After seeing the film, it’s difficult to disagree. A beautifully-staged period piece, “A Dangerous Method” has precious little box office appeal beyond its A-List cast. Sure, there’s a brief scene or two of Michael Fassbender tying up Kiera Knightly and spanking her, but the lion’s share of this period drama is talk, talk, talk (little wonder that the source play by Christopher Hampton is called “The Talking Cure”). In another director’s hands this might be a severe limitation, but Cronenberg, aided by a superb and serious-minded cast, brings to life much more than a bygone era (which is, as I see it, one of the greatest dangers of period films generally) and a portrait of great men and the revolutionary ideas that animated it.

Viennese society on the eve of World War One was a culture that believed in the religion of progress. The radical work of psychoanalysis undertaken by Freud, Jung and Spielrein did much to undermine and destroy that dream by uncovering the irrational forces that guide our lives. For a director whose work so often explores the interplay between sexuality, technology and violence, the marriage of subject matter to sensibility is a perfect fit.

The film is a sober and finely-crafted reflection on the limits of self-knowledge, self-control and even personal honesty. The screenplay (also penned by Hampton) is rarely didactic or preachy and blessedly refuses to dumb down the ideas put forth by the protagonists. In the small genre of films that tackle psychoanalysis, how often can that be said (think of the nowadays laughable Psychology 101 lesson in Alfred Hitchcock’s “Spellbound”)?

Cronenberg has certainly taken a gamble here. With this film he reverses the trend of fast-paced films with mass appeal represented by “A History of Violence” and “Eastern Promises” and delivers a more cerebral film along the lines of “Spider” and “Naked Lunch” (two of his other period pieces), though not as esoteric or visually wild as either. This time, as well, the film’s seriousness works in its favor, unlike the self-important veneer of “Dead Ringers” and “Crash.”

At the center of the film is Jung’s relationship with Sabine Spielrein (Kiera Knightley), a Russian Jewish woman who is first his patient, then becomes his assistant and lover. Michael Fassbender, who is also representing Steve McQueen’s dark sexual odyssey “Shame” at the festival, plays Jung as a frail, tragic figure hiding beneath a facade of noble idealism.

The first time we see Knightley, she is writhing and screaming in the throws of a hysterical fit. As she undergoes a “talking cure” with Jung, she nearly chokes on her words, as they come sputtering out of her staccato and often shouted. Knightley overdoes this at first, but quickly settles into the role of her disturbed but clearly brilliant character. Despite a Russian accent that comes and goes at will, her performance is remarkably surefooted, volatile and courageous and places her high in the running for a Silver Lion.

My greatest misgiving before entering the screening was the casting choice of Viggo Mortensen as Freud. This unexpected bit of casting is wonderfully, unpredictably, successful. This is Mortensen’s third consecutive film with Cronenberg. It feels safe to say that the director brings out the best in him. Here, however, his role is a supporting one. And he brings the cigar-chomping doctor to life in a marvelously understated performance that is animated by intellectual arrogance and the anxiety of losing his authority to a younger colleague.

One of the film’s strongest contrasts is between Protestant Jung, at his sumptuous Alpine estate, paid for by his wealthy wife, and the Jewish Freud, in his cluttered Viennese office. When things go sour between Spielrein and Jung, Freud warns the woman against seeking a blond Siegfried. “Put not your faith in Aryans,” he says. And at this moment, which comes late in the film, you feel Freud’s mistrust of the Christian society around him, a society that has rejected him and that will, eventually, force him into exile. That Mortensen can so convincingly inhabit this quintessential outsider is both testament to his talent and Cronenberg’s firm guidance.