Maureen is a young American in Paris making her living as a personal shopper for a celebrity. Also, she may have the psychic ability to communicate with spirits, just like her twin brother, Lewis, who recently passed away. Maureen soon starts receiving mysterious messages coming from an unknown source.
All about the process of grief and the way thoughts manifest in frightening and uncontrollable ways in the face of tragedy, as well as how Stewart's character learns to cope with her brother’s passing as she descends further and further into a faux reality that’s displayed as a legitimate reality on screen. The whole film is exhibited as a double -- almost presenting, simultaneously, multiple and in a sense subjectively parallel existences (think Kiarostami's Certified Copy). Assayas' peculiar presentation method of a potentially "alternate" narrative makes all of the fantastical elements seem like part of the actuality of the protagonist's situation, rendering her story and character arc immensely ambiguous, and also making it impossible for viewers to know, with certainty, whether what they're seeing is part of the film’s true universe or just the internal mechanics of the way in which the protagonist's mind deals with the loss of her brother and the fear of her own demise.
Fear is but a form of fascination.