Ben and his classmates make a pact to follow the river on their bikes for as long as it takes to learn the truth, but it isn't long before the pact is broken by all except for Ben and (much to Ben's disappointment) Nathaniel, the one kid who just doesn't seem to fit in. Together, Nathaniel and Ben will travel farther than anyone has ever gone, down a winding road full of magic, wonder, and unexpected friendship.