[3] The movie starts in Hell where Satan plans to destroy Christmas by stopping Jesus's birth, and he decides to send three of his minions — Astarotte, Scarapino and Farfaricchio — in Naples from the barrel of Mount Vesuvius since it was the "Crib's capital".

The three devils choose a little kid called Rocco, which is unhappy and jealous for the incoming birth of his little brother Francesco, and he's always angry with his mother and father.

After a lot of tempting, the devils manage to make Rocco say the magic word "Opopomoz" and go into the crib's world, where he's determined to stop Mary and Joseph from coming to Betlem.

Meanwhile, his little Italo-American cousin Sara discovers what happened thanks to Rocco's cat and runs after him into the Crib's world, but doesn't manage to find, and she's found by a young Saint Peter and his family.

Satan's furious with them and decides to kill Mary by hypnotizing Rocco and devouring Sara's soul, but his spell fails after the boy looked at Mary's aureole and the three devils, who are tired of getting bossed and feel sorry for the little girl, wake her and encourage her to sing a song her grandmother taught her which could send away the devil, and so Satan is sucked back in Hell forever.