Petite leçon d'amour (2021)

Julie is a young woman who walks dogs in Paris in her spare time. While walking, she takes shelter in a cafe to escape a rainstorm. In the cafe, she finds a forgotten folder with a math test and a disturbing love letter written by a high school girl to her teacher. Julie frantically embarks on an investigation. She has little time to prevent the worst, because the teenager seems prepared for anything.