It is the early afternoon of a summer day in the 1990s. While their parents are asleep, Lotti and Malibù (nicknames the sisters use for each other) decide to sneak out to a local bar—a spot frequented by the boy they both have a crush on. Puca, the youngest, insists on coming along, threatening to wake their parents with her screaming if they refuse. The three girls set off; as they pass the beach, Puca wanders toward the water’s edge and claims to have seen a mermaid. Once at the bar, the older sisters—preoccupied with their adolescent moods—lose sight of Puca. A search ensues, leading to a confrontation that clears the air between them, followed by a fleeting glimpse of the mermaid diving and vanishing beneath the waves; that image makes them realize their childhood is gone forever. The unexpected happens when they return home to alert their parents…