In a small village in the Piedmont region, nine-year-old Cino lives with his brothers and sisters in extreme poverty. His parents have no other choice than to entrust him into the care of a French carter, who must take him back to France. Once there, he'll put to work in the high mountain pastures of Mercantour. During his journey, Cino strikes up a friendship with Catlin, a girl his age. However, they're quickly separated when she falls ill. Upon arriving in France, Cino is employed by a shepherd. Mistreated by his master, he manages to escape and to get back together with Catlin. The two children then set out on a crazy crossing of the Alps to find their way back home. Their journey will be full of surprises and dangers. The mountain, as though inhabited by mysterious forces, seems to have a magical influence on Catlin...