S01E50: The Imp

Hidden deep in the forests of Moominvalley, an old tree stump has stood for more than 500 years. Leaves have not grown on it for as long as anyone can remember, and yet the old tree refuses to rot away. The elders in the valley remember that there is something special about the tree. One day, Moomin and his friends are playing hide-and-seek near the old tree stump—there is hardly any other place in the forest that is so mysterious—and they discover that there is indeed still life slumbering in the tree's ruins.