Emily and Alexander visit their cousin Wu-Sing in China. He is a friend of the emperor Pu-Yi, who as a child struggles with the old traditions. The mouse emperor Fu-Maus, on the other hand, is known for his courage and kindness. When he suddenly appears in the mouse village and collects taxes that bring the population to the brink of ruin, Emily and Alexander spring into action. They find out that Notail Nogoodnik has kidnapped the real Mouse Emperor and is once again preparing a raid.