Kristen Stewart’s performance drives Personal Shopper, a visually engaging and provoking film that becomes muddled by unconvincing plot decisions and discordant tonal shifts. Personal Shopper marks the second collaboration between director Olivier Assayas and Stewart, after the much more compelling 2014 film, Clouds of Sils Maria.

Again, Stewart plays a kind of assistant; this time as Maureen, a discontent personal shopper for a young Paris socialite named Kyra (Nora von Waldstätten). She has stuck around in the city and in her unfulfilling job only in the hopes of receiving a message from her twin brother who died suddenly from a heart attack a few months ago. The story drifts back and forth between Maureen’s attempts to communicate with her brother in the old, drafty house outside of the city where he used to live, and her running errands for her boss around Paris at Cartier and other high-end boutiques.

The film’s defining features are its musings on loneliness and its inescapability of being alone. The death of her twin robs Maureen of that intangible connection she had remarkably always possessed. Maureen is almost always by herself; she only occasionally talks to a friend over FaceTime, and briefly interacts with others for her work. She skirts around her boss Kyra like a ghost, mostly depositing clothes and other purchases without ever encountering her.

One of the main interactions Maureen has throughout the film is a text message conversation with someone she thinks might be her dead brother. At first, Maureen demands to know who is on the other side of the message, but then she comes to accept that it might be some kind of spirit. Whether or not she decides if the person on the other side of the conversation is indeed her brother, we don’t really know. She laughably asks if he is dead or alive, emphasizing her frustration by sometimes adding two question marks instead of one. Though the conversation is sometimes ridiculous, Stewart plays her role sublimely, portraying a character who is wholly susceptible to the emotional manipulation of someone who may or may not be her brother. From one message to the next, Maureen transforms completely; her wrecked disposition makes us empathize with her, and makes us invested in finding the truth behind the messages.

The messenger becomes much more ominous and harmful over time, culminating in a scene where the spirit appears to creep closer and closer to Maureen. After turning her phone’s connectivity back on, Maureen watches the texts roll in, one after the other, indicating that he will soon be at her door. The suspense of the messenger’s imminent appearance as he comes nearer is excitingly frightening, and delivering this impending doom through the medium of text messages feels like Hitchcock for the 21st century.

The film lacks any sense of irony or awareness about its own silliness. The slickness of the cinematography in contrast to the hokey computer-generated depiction of spirits makes the ghosts not nearly intimidating enough. The horror is much more effective when presented subtly, such as when a ghostly figure is seen in a reflection, a glass shatters from no apparent source, or when automatic doors open without any visible provocation.

Maureen’s obsessions with fear and doing the forbidden are intriguing and key character traits, but the film doesn’t develop them far enough. The film also glances over Maureen’s apparent connection to the spirit world, and the scenes in which she researches into Hilma af Klint and the spirit world through YouTube and Wikipedia are banal and prosaic thriller fare.

Maureen suffers from the same heart malfunction as her brother, which explains her urgency in wanting to learn about life after death. When she finally seems to confront her brother at the end of the film, we are still left uncertain about whether it is really him, whether she is even in a spirit’s presence, and whether he will answer her all-consuming questions about the afterlife. The camera stays on Maureen’s face for the entire scene. Even though the room would appear empty with or without the spirit, the fact that our view is limited to a close-up of Maureen makes us yearn to see her surroundings, and drives home the ambiguity of whether or not she is really alone.

Though the horror aspects of the film and some character decisions are unconvincing or underdeveloped, Personal Shopper largely resists being delegated to a particular genre. The film raises interesting questions while refusing to answer most of them, which is both a frustrating and important role of cinema.