Bearing out that theme most of all are the film’s young actors, all of whom get the opportunity to reveal more than one dimension of character. Wolff, who’s present in just about every scene, manages to hold the center as a young man who isn’t overly concerned about either standing out or fitting in, and whose behavior can often be as hesitant as it is impulsive. But the real find here is Delevingne, an English actress who, with her subtly smoky voice and piercing gaze, makes the girl of Quentin’s fantasies a singularly charismatic presence, all the more so due to her limited screen time. What ultimately happens to Margo may seem somewhat ambiguous by film’s end, but on the evidence of her work here, this striking actress is here to stay.