Riley has spent her life surrounded by boys - that's what happens when your twin brother is Jaden Henline, one of the best baseball players around and the most popular guy in school. As a result, they shared most of their friends, so Riley had almost all guy friends. And up until That Summer, she had never even thought of any of them as more than a brother. But Jaden made it perfectly clear that he didn't want her going out with one of his friends. So she made a vow - a vow to never have feelings for one of her brother's friends. But then her parents announce they're moving to Pennsylvania, and she meets their new next-door neighbor - and Jaden's new teammate - Cole Wagner. And she finds out how just one person can change everything she thought she was sure of.