The ghost movie inspires personal reflection on the experience of losing a loved one, and it may be the ideal vessel for exploring the grieving process.

Olivier Assayas, spilling over the bench beside me, sat up and seized on the momentary silence: “Text messaging is the one modern form of communication. It’s unique. It’s special. It’s something new.”

The same could be said of “Personal Shopper,” which reinvents the ghost story by approaching it with radical directness and a singularly modern sense of self. The movie is among the most affecting depictions of the grieving process I’ve ever seen. And somehow, despite the fact that it includes a scene in which a phantom projectile scream-vomits hot white ectoplasm into the air above Stewart’s face, it’s also one of the most realistic. Bracingly direct one moment and stubbornly elliptical the next, “Personal Shopper” isn’t just a story about a young woman trying to connect with her brother across the beyond, it’s also a story about how technology shapes the way people remember the dead and process their absence. Spiritualists are magnetized to spectacle, so it’s only natural that Maureen is constantly staring at her iPhone, using it to google the paintings of Swedish mystic Hilma af Klint or watch an amusing clip from a (fake) old TV drama in which Victor Hugo conducts a hokey séance. These digital communions lend Assayas’ laconic thriller the feeling of a Russian nesting doll, each layer hiding a new dead body.In the film’s already notorious centerpiece, Stewart’s character is peppered with aggressive, sexually charged SMS messages from an unknown number as she rides the Eurostar train from Paris to London and back again. Stretching between 20 minutes, two countries, and possibly into the afterlife, the scene assumes a sudden new shiver when Maureen begins to wonder if she’s texting with her brother’s ghost, or perhaps a more malevolent spirit.

That the gripping sequence caused such a stir following the film’s Cannes premiere is ridiculous for at least two reasons: For one thing, it may be the 21st Century’s signature episode of Hitchcockian suspense. For another, it’s also the stuff of vintage Assayas, crystallizing what the cinema’s reigning modernist has done so well for the last 30 years.

In “Summer Hours,” three far-flung siblings are forced to negotiate their collective identity when their mother bequeaths them the rustic family estate and a laundry list of keepsakes that have always lived inside. In “Clouds of Sils Maria,” Stewart’s first collaboration with Assayas, middle-aged actress Maria Enders (Juliette Binoche) is as haunted by her own legend and tormented by the next generation of starlets. “Personal Shopper” may be the first time that Assayas’ has explicitly engaged with the supernatural, but all of his movies feel like ghost stories.

So much so, in fact, that “Personal Shopper” might seem a touch on the nose, like David O. Russell making a film about Martin Scorsese or Wes Anderson making a film about tweed. Assayas laughed at this suggestion: “Well, movies are about ghosts! Especially old movies. People became aware of whatever cinema was in the late ’50s, early ’60s, when the first generation of silent actors were gone, and, all of a sudden, you had these movies that were just full of specters. So film has always been the land of the dead.”

Even Maureen’s interactions with the living begin to assume a morbid gloss. She and her far-flung boyfriend speak exclusively over Skype, and every conversation feels like a seance. “It’s like they’re conjuring each other,” Stewart said. The line between the living and the dead feels hazy and permeable, so when Maureen suggests the mysterious texts she’s receiving might be from her brother, it’s surprisingly easy to imagine she could be right.

“People feel so entitled to communication in the digital age,” Stewart offered without a perceptible trace of judgement. “I think mourning has probably changed because we’re so in each other’s faces no matter where we are geographically. Now imagine someone passes away and you’re like, ‘What do you mean I can’t talk to them? I can always talk to them.’”

“I don’t know,” Stewart exhaled, snapping me out of my daydream. “I haven’t had too many friends pass away, and my grandma’s a hundred years old. I haven’t dealt with death a whole lot, and, if I have, it’s been sort of peripheral. I can’t imagine going back and knowing that my entire text thread with this person is still there and they’re not. People’s Facebooks become memorial-type things. I think having this data in our hands all the time, depending on how you approach it, can be really scary because it’s a rabbit hole. It gives you an opportunity to know more than you could remember without it. Is it better to let things go and be affected by them, or always have it there to dwell on?”

For a very long moment, I worried that Stewart expected me to answer, as if that question hadn’t been weighing on me for months. Finally, she let me off the hook:

“Who knows?”

Kristen Stewart is one of the most famous people on the face of the planet, but you’d never know it from talking to her, or from watching her recent movies. It’s been four years since she fulfilled her obligation to “The Twilight Saga” and slipped free from the undead grip of the YA franchise that launched her to stardom. In that time she’s played Steve Carrell’s secretary, Juliette Binoche’s assistant, a young lawyer in rural Montana, a prison guard at Guantanamo Bay, and an anonymous drone in a dystopian society founded upon the idea of suppressing the things that make people special.

She’s been drawn to parts that contradict her outsized public persona, confront the all-seeing eye of her celebrity, and warp it into a lens through which we might all look at her more clearly. “Most people are concentrating on their role and trying to immerse themselves and whatever,” she told IndieWire this past summer, “But I don’t want to lose myself, I don’t want to fall, I don’t want to hide. I want to be seen.”

Looking at her, Stewart is textured with the endearing anxiety that characterizes her on-screen persona. She bites her lip, shifts her eyes, takes each breath without seeming to know where it might take her in return, and at no point did she say something easy at the expense of saying something honest. “It’s more interesting to watch someone figure something out and flounder rather than just regurgitate what they were inspired by,” she blurted out somewhere along the way, doing her best to demystify the appeal that has made her an unlikely critical favorite. “I’ve had to throw myself into things I disagree with or confuse me or make me very uncomfortable — self-hating, sometimes. But because I started so young, I wound up on the other side of some experiences having my mind completely changed. I’ve had some really positive things come out of stuff that initially filled me with disdain.”

I wasn’t about to ask what “stuff” she meant, but she was still quick to shut the door behind her: “‘Forge ahead’ is kind of my motto.”

“Personal Shopper” epitomizes Stewart’s penchant for playing beautiful people who do invisible jobs, a contrast that allows the actress to explore the expressive power of her own vulnerability. The film finds her more exposed than ever before, naked in every sense of the word. When she’s not trying to commune with the spirit of her dead brother, Maureen works for a hostile, high-powered fashionista who seldom appears on screen. She runs errands around Paris and beyond, slipping into (and out of) the clothes she’s picking up for her boss, looking to see if each new costume can tell her more about herself than she can glean from her own nude body.

“Maureen is like half a person,” Stewart said. “She’s lost half of herself.” By night, she looks for that missing portion in the musty corners of her dead twin’s haunted chateau. By day, she looks for it in the mirrors of Paris’ trendiest haute boutiques, and finds herself both intrigued and ashamed by a reflection of femininity that seems newfound, now that her brother is no longer here to balance it out.

“Because we do not know anything about Maureen’s backstory, she’s any one of us,” Assayas said. “To me, she has a normal life, longings, a boyfriend, and then, all of a sudden, the world collapses. I think she’s a blank page.” Stewart vigorously nodded in agreement as the director hunched forward and looked her way. He continued: “She’s on her own with an absence, so she’s a foreigner; the world around her is not her world. She’s in a situation where, really, it’s all about trying to survive, reconstruct herself, find her path, and there’s no interference because she’s on her own, because she’s in a strange land.” It’s unclear if he was talking about the character he wrote or the actress for whom he wrote it.

“I was a shell of a human,” Stewart recalled of the production, her voice crackling with the adrenalized glee of someone who just survived a near-death experience. “It’s funny … there’s a basic, fundamental list of questions that you should know the answers to before you shoot. Not ‘should,’ you actually have to know who this person is before the story picks up. In retrospect, it’s fucking crazy to think about — I knew nothing [about Maureen] that wasn’t in the script, and I didn’t ask. I didn’t think about it.”

“I was such a basic, unencumbered, un-opinionated baby!” She went on, speaking faster with every word. “I knew fucking nothing, and it was a nice feeling. And scary. Definitely precarious. But that’s a nice place to stand. I was only aware of what we were doing after the fact on this, and that’s very personal.”

More personal than her performance in “Clouds of Sils Maria?” Stewart answered without taking a breath, she’d clearly considered this: “It feels more personal because I felt more reduced. I felt like the only way I could’ve ever come to a natural discovery or realization was to deconstruct myself completely.”

If “Personal Shopper” is the movie that Stewart has been working toward, best articulating the casual fearlessness that has become her signature, it’s because none of her other roles have taken her so deep into the unknown. “I wasn’t lost,” she insisted. “I wasn’t so unaware that I was like, ‘I don’t know what I’m doing.’ It’s just that I was so open to not knowing. I wasn’t making a movie anymore. I wasn’t trying to lead anyone anywhere. I was just very aware of the fact that some questions have answers in retrospect, but can only ever be asked spiritually and without words.”

I felt like Stewart was trying to say (without saying) that she was able to portray grief so well precisely because she had never really experienced it for herself. In the moment, that sentiment made all the sense in the world to me, and in the time since — as I’ve wrestled with this film and fought my way through the paralytic fog of trying to write about it — it has increasingly felt like the only honest approach.

Stewart would rather drown than tread water, and Assayas was smart enough to let her jump into the deep end of the pool. “We are on our own,” the director explained of his willingness to strand his leading lady like that. “The process of grieving is lonesome. You can discuss it with your best friend, but it will do you not much good, ultimately. Whatever good can come out of it is something that comes through you.”

What Assayas knew, and what “Personal Shopper” invites Stewart to share with us through her own experience, is that loss isn’t just a process of deprivation, but also one of dislocation. Grief, in my limited frame of reference, is like getting lost on the street where you’ve lived your whole life. It’s a dreadful state of nonsense. It’s not something for which you can adequately prepare in advance. And Assayas’ film respects that — it is pockmarked with ellipses that are never filled, crucial details that are left off-screen, questions that are unanswered as Maureen is slowly thrown back upon herself.

Losing someone is a fact, but it’s a fact that has to be learned like a language. You cry uncontrollably, harder than you have since you were an infant, because you don’t have the words to express how you feel. They come to you, but they come to you slowly and in puzzle pieces you lack the grammar to put together. And when you finally figure out how to speak, when you finally figure out how to take the negative space between all your missing pieces and arrange them into sentences, your only reward is the realization that you’ve been talking to yourself the whole time. What “Personal Shopper” ultimately expresses better than any other movie is that grief begins as a process of reconciling yourself to all the ways in which someone is gone, but it ends as a process of recognizing all the ways in which they’re still here. Still a part of you.

“Wherever we leave Maureen,” Assayas concluded, talking around the powerfully elliptical coda that closes out his new film, “she’s decided, ultimately, that her brother is within her, and that he will stay there.” The director thought about that for a moment, turning the words over in his head. “You’re really on your own with grieving.”

But thanks to films like “Personal Shopper,” that’s not entirely true.

On a long-enough timeline, every movie is a ghost story.

I watched “Personal Shopper” again after speaking to Stewart and Assayas. I thought about how Maureen convinced herself (and me) that she was receiving texts from the afterlife, about all the ways in which she attempts to contact her dead brother, and it occurred to me that this is a film about a woman who thinks she’s looking for a doorway, but spends most of her time staring into mirrors. Maureen might be able to see electrical ghost energy as it crackles around a darkened hallway, but she’s more haunted than any of the houses that she’s hired to investigate. She sees her brother within herself, and everything else is just a trick of the light.