Marie has always been somewhat independent and is considered by some to be a bit of a tomboy. Though she is not quite a teenager, her photographer father has no qualms about leaving her alone for a while when he has to go off on an assignment. One day, while she is walking along, she gets run down by an automobile. The contrite woman driving that car sees to it that she is all right, and before long the two of them have become fast friends. Lilas, the driver, is a prostitute, and she discovers that she has a thing or two to teach the kid about femininity and men. Before long, the precocious youth is trying out her newfound powers of seduction on a family friend.

Lilas, une prostituée, travaille dans une contre-allée de l'avenue Foch. Un jour celle-ci renverse Marie, une petite fille de douze ans qui habite l'avenue. Le père de la fillette, un grand reporter, la laisse très souvent seule, Marie se met a observer Lilas, et décide d'aller lui parler. Une amitié naît alors entre la femme et la fillette...