When the kitten Binou accidentally soils his favorite doggie, Mr. Mou, the mouse Toupie (Marc Labrèche) calls on Dorothée (Anne Dorval), a cow living in a magic lamp, to get rid of the stain. However, because of a misunderstanding, it is the whole doggie that disappears. Toopy, Binoo and Dorothy must therefore go to the World of Lost Objects to find the precious stuffed animal. During this incredible adventure, the trio meet two gull twins, Jacques-Henri (Xavier Dolan) and Jean-Jacques (Stéphane Rousseau), who are looking for their dad, as well as the mare Magnifique Princesse (Geneviève Schmidt), whose dance partner has disappeared.