Julien is a grumpy man, who lives alone in a large apartment in Paris. He devoted all his life to collecting butterflies. Isabelle and her daughter Elsa move in next door to him. Isabelle works as a cashier in a supermarket and prefers having fun instead of taking care of her little daughter. Every nigh Elsa is left alone at home. One evening she meets Julien and claims: “If my mother leaves me alone I will run away with you!” Julien ignores her and sets out on his annual attempt to find a rare species of butterfly called “Isabelle”. But he has no idea how smart Ella is. So the adventures of little Elsa and Julien begin.