In Boston, Emily and Alexander visit their cousin Casey, who is an avid baseball player. And as luck would have it, the very first America-wide national championships in baseball are also taking place. However, there is a small problem: the best player of the Boston team has lost his lucky charm, a four-leaf clover. Now all his courage is gone, because he is very superstitious. Our clever mice immediately set out to find this special lucky charm and slip right into a new adventure.