Two sisters, 12-year-old Anaïs and 15-year-old Elena, go on a family vacation to a seaside resort in France. Both girls have contrasting personalities and appearances: Anaïs is overweight and introverted, while Elena is slim and attractive. During their stay, Elena becomes involved with an older Italian law student named Fernando, who seduces her, despite their parents’ strictness. Anaïs, often overlooked, becomes an observer to her sister's romantic dalliances, harboring her own complex feelings of jealousy, curiosity, and protectiveness.

The story delves into the sisters’ intimate conversations and Anaïs's struggle with her own burgeoning desires and self-worth. Tensions rise as the sisters navigate their conflicting emotions and the impact of Elena's relationship with Fernando. Against the backdrop of a seemingly idyllic vacation, themes of sexual awakening, sibling rivalry, and the harsh realities of adolescence are explored. The narrative critically examines the vulnerabilities and psychological landscapes of the young protagonists as they grapple with the challenges and consequences of their experiences.