The Little couple decide to visit an orphanage to adopt a new member of the family - what they didn't even imagine was that the chosen one would be a small and charismatic mouse, called Stuart. But in addition to the couple's son's resistance to his new brother, the family cat is even less enthusiastic about the idea, planning a way to get rid of him. Dealing with all of this in the process, Stuart will realize that his encounter with the Littles will change his life, in a way that as he had already stopped believing.
