Antoine and Laurent, old friends, spend their vacation in Corsica with their respective daughters: seventeen-year-old Louna and eighteen-year-old Marie. One evening at the beach, Louna seduces Laurent. Louna is in love, but for Laurent it was nothing more than a momentary distraction. Without revealing her lover's name, Louna confides in her father, who tries by any means to discover who his daughter's lover is.