Ten-year-old Nicki Fleming is about to start fifth grade. She has spent the summer on her Colorado ranch working with Sprocket, the service dog she has been training, and helping her mother, who is expecting twins. In addition, Nicki's best friend Becca was away all summer, and Nicki has gotten to be close friends with Kris, one of the new girls at their school. The start of a new school year is usually an exciting time for Nicki, but this year it's laced with sadness because it means that Sprocket will soon leave for advanced training and eventual placement with a person with special needs. Starting school is also more challenging this year because it means trying to maintain close friendships with both Kris and Becca, who don't know each other very well. Can Nicki find a way to let Sprocket go AND to keep both Kris and Becca close?