Claire Denis shakes with laughter when I pander to her auteur reputation and suggest that she must be a very intense person to capture such extraordinary images. “I’m laughing,” she says. “But it is true that I have to be, let’s say high, on the set, really believing that I’m filming something that conveys an emotion, that the scene is alive for me, not just a reproduction of an emotion created while writing the script.”

The 57-year-old French director’s work is always raw and fresh, even when it’s structured unconventionally and difficult to digest. Which is the case lately: her most recent film, L’Intrus, takes place half in the northern hemisphere and half in the south, and dallies almost equally between reality and fantasy.

It concerns Louis Trébor (Michel Subor), a sixtysomething loner who lives in a cabin in the French Jura and maintains a frosty relationship with his son in the nearby town. He needs a heart transplant; there are dark, obscure intimations about the lengths he goes to secure a donor. He’s menaced by a strange, beautiful Russian woman with secrets from his past. Post-op, he clings desperately to his new lease of life and heads for Tahiti in search of another son he abandoned.

L’Intrus has the same lucid, sensual eye as Denis’s one rubber-stamped masterpiece, the 1999 Foreign Legion drama Beau Travail, but also an oblique narrative that will split audiences as surely as her other movie’s core of immaculately choreographed beauty united them.

Not that that seems likely to faze the director, who knows exactly why she had to make the film. It was, she says, inspired by the physical sensation she experienced after reading Jean Luc-Nancy’s L’Intrus, a 40-page account of his heart transplant. “Reading it, I suddenly felt my heart in that cage, because he said the ribs were like a cage.”

Unlike Nancy’s, her heart was still her own, but she leapt on the theme of foreignness and started erecting a narrative around it.

Trébor was, says Denis, almost a direct tribute to something she perceived in Subor himself. Denis talks about the veteran actor as a womaniser and a nomad, but “I always thought he was a lonely heart, a broken-heart guy. Something was intriguing about him: his secret, you know.”

Subor has since said that working on L’Intrus has changed him; he almost bought the house Trébor starts the film in, and kept the character’s huskies.

For the most part, though, Denis has no time for finicky psychological explanations: “When it ends up on the screen, very often it ends up there clumsily.”

Instead, she talks about the work of the cast and crew as a set of overlapping performances, with herself as a facilitator. She prefers “mise en scène” to “directing”, as it lacks the puppetmaster connotations (later she refers to “my editor”, then corrects herself: “Sorry, the editor”).

Unsurprisingly for someone whose films always engage with the textures of the modern world, she’s also inquisitive about other cultures. A recent foray into the ballet world, filming the documentary Vers Mathilde with the choreographer Mathilde Monnier, had unexpected results for both of them. Denis encouraged her reluctant friend to loosen up and try dancing to PJ Harvey. Now Monnier is performing publicly to the music; Denis is hoping to team her up live with Harvey.

In everything she does there’s something impressively alive about her. “There must be something happening,” she says. “Maybe it’s very tiny: the camera rolls and it’s not happening, then a dog barks or a cloud comes over. But something happens and suddenly everyone wakes up.”

The Claire Denis retrospective is at Ciné Lumière, the French Institute, 17 Queensberry Place, London SW7 (020-7073 1350), from Oct 7-12

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