An impish, stick creature called Leaf lives in a giant, old tree beneath an ancient volcano and its melting glacier. One day, Leaf's young brothers run away to play in the vanishing snow, but soon the Twig twins are lost in a maze of endless ice tunnels. With the help of a grumpy hermit and feisty pika, Leaf searches the blue tubes. But it is the rare beasts of the Long Ice who will decide their fate