On the day that her father is set to move out of the house, Margaret runs away to live in the local amusement park, Foreverland, a place she associates with happy memories of family visits. But there's someone already living there—a mysterious boy named Jaime.
Amid the thrills of spending the night hiding out in the park, Margaret learns to take charge of her life and become more self-confident. As she and Jaime become friends, she learns his family secret, and then they help each other find their way home.