Alder has always lived in his cozy little house in Southern California. An old, reliable, comforting walnut tree has stood between his house and the one next door. When a new family--with a particularly annoying girl his age named Oak--moves into the neighboring house, they cut the tree down. As Oak and Alder start school together, they can't imagine ever becoming friends. But they soon discover a series of mysterious, possibly magical, connections between the two of them.