As Christmas approaches in Naples, little Rocco feels increasingly jealous due to the imminent birth of a baby brother. His young parents don't notice his unhappiness, but three little devils sent to earth by Satan single fim out for a special temptation. The devils promise Rocco if he will stop baby Jesus from being born on Christmas Eve by saying the magic word "opopomoz" and thereby entering the elaborate Nativity scene his father built, his brother will never be born and he will remain an only child.