Léo Polatouche is a flying squirrel. He and the rest of his family form an acrobatic troop. Travelling by barge along rivers and streams, they set up their circus tent here and there along the way in clearings in the woods. Léo has a problem though : he is much smaller than his brothers and sisters, and, because one of his paws hasn’t developed normally, he can’t maintain his balance on the high wire. He is different from other squirrels.

After the final show of the season—a real disaster—Léo’s father is angry and his mother even seems a little disappointed. Léo runs off hoping the others will worry and eventually come looking for him. However, through an unforeseeable series of tragic circumstances for which he feels responsible, Léo is separated from his family. He is afraid they may even have knowingly abandoned him. He’ll find refuge underground in a house owned by Mr. Griffon and Mrs. Mélodie, a couple of moles who will watch over him.

Throughout the winter, Léo will have to live underground in unfamiliar surroundings, far from sunlight or even the sound of rain. He’ll experience a complete range of emotions, from anger to guilt, from sadness to anxiety, from excitement to despair. He will also discover a different way of life and much about himself.