Cry of the Lizard (1991)

A group of teens leave their comfortable homes on a trip south to the Pyrennes Mountains in order to find a treasure that they have read about. Simultaneously, a fourteen-year-old boy has grown so fixated on Clo (Andréa Ferreol), a mature woman, that he has run away to be with her. After treating him appropriately for his age, she follows her own curiosity and they briefly engage in a sexual relationship, after which she resumes her role as an adult and sees to it that he returns to his family, which has been suspicious of their relationship all along.