Carrie's life has taken an unexpected turn. Since her last great adventure, her dad has moved out and remarried. Her mom will spend the summer in Miami, which leaves Carrie to learn how to live with her step-mom and a new step-sister. Mrs. Huffity gives Carrie a bit of advice about her new little sister, Shannon.
When Mrs. Huffity is involved, there is bound to be an adventure. This time is no different. Shannon and Carrie are in for the summer of their lives. And Carrie discovers Shannon's secret, a secret that affects both their lives...