This book is about a girl named Laurie Stratton, how she finds out she has a twin, tries to find her, and the problems that ensue. The characters are the kids from school, Laurie's boyfriend Gordon Ahearn, her next boyfriend Jeff Rankin, her best friend Helen Tuttle, her brother and sister Neal and Megan, her parents, and her twin sister Lia.
Laurie starts out by telling how every girl has that special summer in which she changes from immature girl to young lady. The past summer was the one for her. She would normally spend her summer days hidden behind a book, all alone. This time, when she stepped out onto the beach, she got her first wolf whistle. It was two guys from school. Next thing she knew, she was going out with Gordon Ahearn (one of the most popular guys at school) and hanging out with his group of friends.
One of them was Natalie Brighton, whose father owned the Brighton Inn. She decided to through an end of the summer party. Right before the party, Laurie caught the stomach flu and couldn't go. The next morning, on her way to the ferry (since they live on an island, they ride a ferry to the mainland to go to school), she waved hi to everyone, but got a strange reaction. She was told that Gordon and Natalie saw her on the beach when she was supposed to be at home sick. She was completely confused because she was sick at home vomiting everyone hour or so.
The first day of school was basically the same as always. She met her new teachers, found her classes and met her new locker mate, a south- western girl named Helen Tuttle. They found that they had the same split period...