Lucas is an 8-year-old boy who wants to know how Pérez is able to exchange teeth for coins without any kids noticing. When he attempts to satisfy his curiosity, Pérez is trapped by Gil Penkoff, an unprincipled entrepreneur who seeks fortune by selling Pérez' secrets to the world. Lucas and his family have to do the impossible to repair the damage and enable the Kindest Mouse in the World to continue in his mission to make children happy.
