“Young & Beautiful,” the latest movie from French director François Ozon, begins with a shot, through binoculars, of a young woman sunbathing topless on a beach. Voyeurism is clearly on the agenda, and Ozon seems to be teasing out some of its creepy implications when he reveals that the binoculars belong to the sunbather’s younger brother.

But what is most striking about this movie is how unselfconscious it is as it conducts a prurient and superficial inquiry into adolescent female sexuality.

Isabelle (Marine Vacth), the girl on the beach, is about to turn 17. On vacation with her mother, stepfather and nosy little brother, she loses her virginity to a German guy. She seems a little bored by him and by the experience, as she does by most things.

We follow her through four seasons, each one introduced by a Françoise Hardy song, but pop-music romance is not really Isabelle’s thing. Instead, she greets the new school year by going to work as a prostitute, advertising her services online and arranging to meet mostly middle-aged clients in hotel rooms around Paris.

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Vacth’s face sometimes suggests a very young Julia Roberts, though the portrayal of sex work in “Young & Beautiful” has more in common with “Belle de Jour” than with “Pretty Woman.” Or it would, if Ozon, who wrote and directed, had figured out where he wanted to go with his premise.

“Young & Beautiful,” though it occasionally nods at the comic and melodramatic potential of Isabelle’s story, opts for a tone of suave detachment. There are a few moments of near-intensity — when a client dies, when Isabelle’s mother discovers her daughter’s after-school activities — but the mood is dull and quiet.

Isabelle is reluctant to explain her actions, and Ozon declines to explore either the psychological sources or the social meaning of what she does.