Toby and his friend Lucas made a list of things to do the summer before they entered middle school, but now Lucas is gone, and Toby sets out to fulfill the promise he made to his friend, to finish the list by hiking the Appalachian Trail from Velvet Rocks to Mt. Katahdin, an undertaking that he is poorly prepared for--and which will become not only a struggle for survival, but a rescue mission for the starving and abused dog who he finds along the way.