Iris and Ariel are 17-year-old twins, who live with their mother and older sister in an old house in the middle of a rocky island covered with molluscs and birds. The teenagers have grown up isolated from the mainland, in a sibling relationship that surpasses the limits of normal intimacy. The abrupt absence of their mother deeply wounds the three siblings, and Iris, moved by a strong need of separating herself from her brother, decides to go alone to the city for the first time.