In A Dangerous Method, Keira Knightley is a lunatic—and I’m not just talking about her character. Within the first five minutes of David Cronenberg’s latest, it’s clear that although she co-stars with Viggo Mortensen and the currently ubiquitous Michael Fassbender, Knightley is who you’ll talk about as you leave the theater. In this film adapted from a play (adapted from a book) called The Talking Cure, Knightley plays Sabina, a Russian Jew who in 1904 is sent to a Swiss institution run by therapist Carl Jung (Fassbender). And she’s a piece of work: Screaming, laughing, sputtering and stammering, contorting her body and jutting her jaw, Sabina seems less a mental patient than someone transforming into one of the Walking Dead. She can’t answer a question without a physical interruption, typically a protrusion of her lower lip into what, accompanied by a fierce eye roll, looks like the Underbite of the Damned.

Sabina’s emotional affliction is sexual. Her father used to beat her, and since then any hint of humiliation turns her on. Even when Jung hits her coat to rid it of dirt, Sabina twists her body into a corkscrew, her hands hovering near her lady parts. Girlfriend’s got it bad. But is she crazy?

Apparently not so much, because Knightley’s antics settle down as the film settles in. But then, unfortunately, the Talking Cure becomes the Talking Curse. Except for Knightley’s whacked-out performance, there’s not an ounce of Cronenberg in this Cronenberg; he directs without visual flair or distinction, turning in a pedestrian drama about an interesting period of history, when Sigmund Freud (Mortensen) developed the methods of psychoanalysis. That’s the approach Jung takes with Sabina, sitting behind her as he asks about her feelings. Soon Sabina is “sane”—if still stilted and a bit weird—and well enough to assist Jung’s research. (She wants to become a doctor.) As portrayed, it’s a bit of leap.

So is the film’s nine-year timespan. A Dangerous Method jumps years at a time, with little to explain the passage of time save text that says so. Throughout, we get talking—and talking and talking and talking. Jung, who didnot know Freud when he began practicing psychoanalysis, pays him a visit in Vienna two years later, and the pair become friends. After that, it’s a lot of letter-writing. Oh, and the affair: Encouraged by a bon vivant patient, Jung begins sleeping with Sabina while his wife keeps on having his children.

Their lustful trysts are missing one thing, though—the lust. You never quite believe Jung aches for Sabina the way she aches for him. And considering their relationship is a significant chunk of the film—most of it, actually, interspersed with psychoanalytical shop talk—that’s a major fail. Another question mark involves the analysts’ glacial falling-out, with Freud claiming that he can’t abide Jung’s “second-rate mysticism and self-aggrandizing shamanism.” Um, what? All they’d been discussing to this point is—surprise—the sexual meaning behind every action and dream. (The man famous for saying “Sometimes a cigar is just a cigar” always has a cigar in his mouth.) When exactly mysticism entered the conversation is anybody’s guess.

Even at a mere 99 minutes, the film plods on. Fassbender is unremarkable here, as is Mortensen, although the latter’s careful, clipped, smooth enunciation at least makes for easy listening. You become less and less interested in Knightley as the story wears on. (The she-wolf becomes a scholar? Really?) In the end, the only thing this kind of talking will cure is insomnia.