Romy is enjoying happy days with her best friend Hatchi-Ping, but she often argues with her mother (Velita) about the difference between what she wants to do and what she has to do. Then one day, following an incident that shakes the sea, her mother disappears without a trace into the ocean. Romy loses her mother without being able to offer even a single apology or a hug. Facing the sea for the first time, Romy gathers her courage with her best friend Hatchi-Ping, the sea boy Kite, and three Tinipings. They must confront the dazzling underwater city and giant deep-sea creatures. Finally, Romy uncovers a secret her mother never told her.