It takes place a couple years after the end of Dear Mr. Henshaw, and Leigh Botts has grown a lot. One day, while walking on the beach, he and his friend, Barry, find a stray dog who they name Strider. They each share custody of the dog, in the same way divorced parents share custody of their children (Leigh is never given into the custody of his father). However as time goes on Barry takes care of the dog less and less, which causes trouble for Leigh until he takes full custody. He joins the track team, and has a crush on a girl with red hair.