In “Young and Beautiful,” Marine Vacth plays Isabelle, a French teenager who turns to prostitution for reasons that are never really explained. (Sundance Selects/IFC Films)

It’s probably not a good sign that Isabelle, a French teenager on summer vacation, has what seems to be an out-of-body experience while losing her virginity to a cute German on the beach. The visual metaphor in Francois Ozon’s strangely dispassionate “Young and Beautiful” — in which the character appears both to watch herself being deflowered and to watch herself watching — seems less an indication of emotional detachment than the onset of serious mental illness.

The smoke has barely cleared from the candles on Isabelle’s 17th birthday cake before our dewy young heroine (Marine Vacth) finds herself back in Paris, inexplicably turning tricks after school at 300 euros a pop.

You might wonder, at 15 minutes in, whether a chunk of celluloid somehow went missing. I certainly did, until it became clear, as the movie wore on, that Ozon isn’t interested in explanations, psychological insights, lessons, judgments, diagnoses, or any of the other stuff that normally preoccupies storytellers.

The filmmaker does, however, seem unusually interested in the mechanics of sex. There are lots of shots of a naked 22-year-old Vacth — who looks closer to her character’s age — engaged in various sex acts, mostly with much older men, whose predilections tend toward the sadly predictable.

Why Isabelle becomes a prostitute is the film’s enduring mystery, and no typical explanation makes sense. She certainly doesn’t need the money. Her mother and stepfather (Géraldine Pailhas and Frédéric Pierrot) give her everything she needs. It doesn’t look like empowerment either, given the misogyny Isabelle must put up with. Teenage rebellion? An attempt to feel grown up? Peer pressure? Addiction? Nothing seems to fit. Even the most obvious answer — pleasure, given a masturbation scene early in the film — doesn’t correspond with the expression of sullen tedium on Isabelle’s face before, during and after every liaison.

When Isabelle’s mother finds out — courtesy of detectives investigating a client’s death by heart attack — her disgust at her daughter’s behavior actually seems reasonable. Isabelle is a singularly unappealing character, with little that might engender sympathy. Despite being young and beautiful, as the title says, Isabelle comes across as “bad to the bone,” to quote her mother.

So what, then, is “Young and Beautiful” ultimately about?

It’s not an exploration of adolescent female sexuality. Ozon is clearly more interested in what makes Isabelle’s wrin­k­led clientele tick (Viagra, in one case) than he is in her. Although her relationship with one white-haired customer (Johan Ley­sen) is mildly touching, it’s almost entirely because of him, not her.

After Isabelle quits, there’s a glimmer of hope that she’ll learn how to develop healthy relationships. She even meets a nice boy (Laurent Delbecque) whom she seems, briefly, to fancy.

But Ozon has created a monster that he can’t seem to let go of. Isabelle doesn’t just frighten her mother (and us). She seems to terrify Ozon, and I’m not sure I want to know why.


Unrated. At Landmark’s E Street Cinema. Contains sex, nudity and crude language. In French and some German with subtitles. 95 minutes.