Mabel Stanley (Kristy McNichol) is an introverted and bookish teenage girl from the United States in a seaside community in Australia as an exchange student. She attends a local pirate festival featuring a swordplay demonstration led by a young curly-haired instructor and fellow American (Christopher Atkins), who then invites her for a ride on his boat. She is duped by her exchange family sisters, Edith (Kate Ferguson), Kate (Rhonda Burchmore), and Isabel (Catherine Lynch), into missing the launch, so she rents a small sailboat to give chase. A sudden storm throws her overboard, and she washes up on a beach.