Plenty of writing on writer/director Olivier Assayas’ latest collaboration with Kristen Stewart (after 2014’s Clouds of Sils Maria) suggests that it’s about grief, but it seems just as possible to see it as mostly about fear. Both interpretations work for Assayas’ slippery sui generis story, in which an American would-be artist named Maureen (Stewart), working Paris as personal assistant to a high-maintenance socialite, begins to believe that she’s receiving communication from her recently-deceased twin brother. There’s no question that something supernatural is going on; Assayas includes literal ghostly apparitions in a story that tangles up psychological drama with horror and crime thriller. It’s a bumpy ride with odd false climaxes, sparked by occasional sequences in which text messages provide an improbable jolt of tension. But Stewart’s performance, playing on her unique mix of strength and tentativeness, carries the story through its ambiguities and unevenness. The pain of coping with a loved one’s tragic death certainly resonates, though that might not be as potent as the need to believe in a happy afterlife because of what it means to one’s own mortality.