Seeking to win the eternal battle between Good and Evil, Satan charges three little devils—Farfaricchio, Scarapino, and Astarotte—with preventing the birth of Baby Jesus on Christmas Eve by exploiting the dark thoughts of humanity. The three single out Rocco, the son of a Neapolitan nativity-scene maker, to carry out their mission. Jealous of the little brother who is about to be born and who has become the focus of his parents’ attention, Rocco is driven by resentment. Upon uttering the magic word “Opopomoz,” he suddenly finds himself inside the nativity scene, where he sets out to prevent Joseph and Mary from reaching Bethlehem. But his lively young cousin Sara follows him there, determined to thwart the diabolical plan.