The party line on A Dangerous Method is that it is more of a period piece - and a sort of biopic to boot - than it is a David Cronenberg picture, and that whatever its relative success or failures, we'd all be better off with a little bit more heads exploding and nightmare gynecology, and a little bit less of gentlemen in the early 1900 furrowing their brows as they read a letter recited in voiceover by the letter writer. And speaking as a fan of the exploding heads period of Cronenberg's oeuvre, I'll admit that I really do miss those movies, but it doesn't appear at all likely that he's going to be returning to them anytime soon, so it's not going to do any of us a lick of good to sit around and sulk about it.

More importantly, I wonder if that verdict isn't a little off-base; A Dangerous Method is maybe not so hugely fucked-up by the standards of a Cronenberg movie, but it is awfully fucked-up by the standards of a dry pre-WWI biopic, and in some awfully subtle ways at that. I am sure it wasn't the director's intent, but while watching it, I was frequently thinking of the film not in the context of 2011, where it's awfully hard to get a handle one what the hell it wants to be, but of the Paul Muni vehicle this might have been if this same story were told in 1935, which - graphic sexual conversations aside - it easily could have been. It's probably stretching the movie too far to suggest that this is essentially one big experiment in creating a film that would have been "Cronenbergian" in the period in which it is set, but it's an idea that I haven't been able to shake ever since I first had it. At any rate, it is (if I am not mistaken) the director's first true costume drama, and it's only fair that he should get a chance to play around and see what that means for him as an artist.

The plot is just about as irritatingly high concept as it gets: from 1906 to 1915, Zurich psychoanalyst Carl Jung (Michael Fassbender) and his mentor, Viennese psychoanalyst Sigmund Freud (Viggo Mortensen) were in close correspondence, met and formed a wonderful working relationship, and eventually stopped speaking or having anything to do with one another's theories. Officially, this is because Jung's belief in metaphysics rankled Freud, while Freud's insistence on reducing everything to the sex drive frustrated Jung, and screenwriter Christopher Hampton (adapting his own play The Talking Cure along with John Kerr's book A Most Dangerous Method) doesn't exactly not say that this was the case, though he's also content to suggest that the really real reason was, as always, a woman (though not in quite the way you might think); and moreover, that the woman, Sabina Spielrein (Keira Knightley), deserves a lot more credit than she is accorded in the development of psychotherapy in the early 20th Century.

As period pictures about world icons go, this is fair stuff - Hampton, the playwright and screenwriter behind the superlative 1989 Dangerous Liaisons knows his way around fussy, talky movies with arch dialogue - and it even manages to avoid, mostly, the dreaded Biopic Dialogue, in which otherwise functional writing sounds weird as hell because it is being addressed to or from famous people. There's a bit of a reek of prestige picture airlessness to it, maybe - while it doesn't precisely lack insight into Freud, Jung, and the world of early psychoanalysis, it's fair to say that the script doesn't exactly stray from what the average person could be plausibly expected to know about those men, though its foregrounding of Spielrein is certainly a nice bit of cinema-as-history lesson.

The difference between "fair stuff" and "damn, that's a good movie" - and damn, A Dangerous Method is a good movie - lies in a lot of tiny things that are just a little bit kinky - there's a sex scene that is, as such things go, just barely in R-rated territory, and yet it feels peculiarly transgressive, thanks to the setting and the fact that it's jarring to see an actress of Knightley's stature topless - just a little bit dysfunctional - the scene structure of the first half of the movie especially is arrhythmic in a manner I can barely describe, but the way that time is glossed over and years passed in a single cut gives the whole thing a disorienting charge that, after great consideration, I have decided that I liked - and just a little bit self-mocking, especially in Mortensen's marvelous Freud, an incredibly amused, plummy sort who doesn't seem at all like the serious intellectual the script otherwise demands.

Mostly, though, it works because of Knightley's performance, and how much of this is her choice and how much is Croenenberg's direction, I cannot say, but this much seems true to me: she is the hinge on which the entire project pivots, twisting a smartly-made biopic into a sometimes freakish and sometimes brilliant study of human neuroticism and sexuality by dint of existing on an entirely different plane than the rest of the movie. Honestly, all three leads seem to be operating in different, incompatible modes, and this is so well-supported by the script that it never once seems to be a problem; but Knightley in particular is in some strange gonzo register where a broad, what-the-hell accent and peculiar physical mugging, particularly in the opening scene which is all about her character's insanity, communicated here by having Knightley thrust her jaw out as far as it will go. It is a performance that is, and probably should be divisive; it is in no way whatsoever a classically good piece of film acting.

But that's exactly what makes it such a wonderful fit for A Dangerous Method, which is after all a movie about psychiatry; if Hampton and the male leads represent the safe, descriptive side of that, the history and narrative and the like, Knightley and Cronenberg are the warped, dangerous, erratic side. Knightley's performance is effective precisely because it is so unpredictable and alienating; she single-handedly turns the movie as a whole into a deranged chamber piece (she is maybe not onscreen more than Fassbender, but she is surely the film's central character). Obviously, without such closely-observed filmmaking all around, and without the sedate Fassbender performance to represent normalcy and convention, Knightley's work would have no place to function, but as it stands, she provides exactly the jolt of electricity that makes A Dangerous Method so much more than just a tale of feuding doctors; it is is a film about the uncertainty of the human brain, and having a rule-breaking central performance is an ingenious way to communicate that theme directly and with great potency.