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.