Juliette Binoche has been in what they call the "zone" for some years now, basically delivering near-flawless performances in film after film. Whether she deserves any credit for Kristen Stewart's equally fine and rather revelatory work in "Clouds of Sils Maria" -- raising the bar, perhaps, or just being an inspiration to her younger co-star -- the two women make Olivier Assayas' provocative drama one of the finer films the French director has made. And he's made quite a few.

It's another director who haunts the proceedings, though, namely Ingmar Bergman, whose intimate naturalism Assayas seems out to replicate, and salute. The world-renowned Maria Enders (Binoche) has traveled to Switzerland to accept an award to Wilhelm Melchior, a famously reclusive director-writer whom she credits with making her career. Just before showtime, news arrives that Melchior has died. What was supposed to be a celebration turns into a memorial. And what seemed to be a quasi-satirical story about life among the ultra-privileged becomes a study of female relationships, and some outrageous border jumping between fiction and reality.

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Stewart plays Maria's personal assistant, Valentine, and, in addition to bringing enormous dimension to the character, makes her a constant surprise. Some of that may be the audience's fault: We probably expect the "All About Eve" scenario we don't get; we might assume that Maria and Valentine are faced with the same lesbian attraction contained in the play Maria is set to do, a remake of the Melchior play that made her famous -- in the younger role, now being played Jo-Ann Ellis (Chloë Grace Moretz), who is as celebrated for her tabloid scandals as her movies.

The most exhilarating sequences are where Maria and Valentine rehearse lines from the play, walking around beneath the Alps, or in their house, obliterating the boundary between fiction and their lives. You hardly know where you are, except in the presence of two actresses at the top of their games.