PERSONAL SHOPPER is a great film by Olivier Assayas and Kristen Stewart is great in it. It follows upon Assayas’ Clouds of Sils Maria, also with Stewart, a great film too and parallel in structure. PERSONAL SHOPPER swaps out the fictional for the supernatural or implies, perhaps, that the two are one and the same. They both suggest, PERSONAL SHOPPER in a metaphysical sense, overlapping realities, and each refuses, like the universe itself, to confirm or deny the overlap. PERSONAL SHOPPER is a puzzle in which the pieces almost fit, but when they are jammed together, one is missing, or, maybe, there is one left over.

Yet PERSONAL SHOPPER is no game. Reality is a deadly affair. Stewart has the last frame of the film, before it fades to white, and her tears are those of any who are touched by the unknowns of existence. Are there others, or has it just been me all along? To call it a “supernatural thriller” or a “ghost story” isn’t wrong, but PERSONAL SHOPPER is not reducible to genre. I’m not even sure it’s an “art film”: for no clear reason is it not a big screen sensation. What it is is beautiful, profound, gripping, moving, thought-provoking, and hard to write about. To recount the thoughts it provokes risks spoilers, for they comprise its texture and maintain its suspense.

But to state some basics: Stewart is an American living in Paris and working as a personal shopper for a self-absorbed fashionista named Kyra (Nora von Waldstätten). When we hear Stewart’s full name, Maureen Cartwright, it is like a joke, so mercilessly Middle American does it sound. She has a boyfriend in the Emirates, Gary, working on security protocols for a computer system, who Skypes in at awkward times (Ty Olwin). She won’t join him because she is waiting for her twin brother, Lewis, with whom she shared both a heart defect and the abilities of a medium, to contact her from the afterlife. She is expected to certify that his house, up for sale, is free of ghosts and gets involved with a criminal subplot. Meanwhile, on her cardiologist’s advice, she is to avoid strenuous activity and intense emotion: PERSONAL SHOPPER, serious though it is, is witty and playful.

The film, however, is about more. Maureen has an inner life (and an outer one) deeper than the bare plot. She is beset by crises of identity cultural and spiritual, and she questions the duality of existence despite the evidence of her six or more senses. None but Stewart, for whom it was written, could play the part so well. There’s a tremulousness in her, and a strength to calm it, a grasp of the everyday in the face of the void (she might as well, in that respect, be French). She is, in an instant, both certain of herself and doubtful, anchored in her being but suspicious of its reality. Her questions become ours, or ours hers. Stewart’s “whatever” mode (you hear her saying it just to look at her) could not be more perfect for a film about existential doubt.

There are devices in PERSONAL SHOPPER consistent with how the supernatural is conventionally portrayed: ectoplasm taking shape in the dark, objects held in mid-air by unseen beings, doors opening and closing, ethereal sounds in response to human actions. Maureen is stalked by texts that may or may not have been sent by a living person (her phone should be on the cast list). But even the most familiar conventions, which we think we understand because we’ve seen them before, are shadowed by ambiguity. Flashes of insight, when we think we’ve put the story together, are contradicted after, then reaffirmed, maybe. Stewart, the insouciant seeker, gives us a Maureen who shapes, and mirrors, our doubts.

We think we know how ghosts and humans see each other (were both to exist), but do we? Are they as afraid of us as we of them? How would you react if you saw a ghost? How would a ghost react to you? These are, however fanciful, analogues to what we can ask about legitimate reality. I imagine there are some who, at the end of PERSONAL SHOPPER, think they have “solved” it. Perhaps. I like a scenario that makes near sense, but there’s a piece missing, or an extra one, who knows which.

Every shot in PERSONAL SHOPPER is exquisitely composed, and the cinematographer Yorick Le Saux lends a soft and delicate beauty to it all. Effects that would be hokey in a lesser film expand the visual field in this one. This is a movie, by Assayas, and a performance, by Stewart, that opens eyes and challenges them to see.

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