Four trolls work their best magic to help Karina's father, who has been accused of stealing the priceless Golden Tsarina Egg. The only clue to the real thief is a trail of chocolate candy wrappers. Karina and the trolls must outwit the evil Mr. Big, who will go to any lengths to get the marvelous Egg's treasure.

The f Norfins encounter a friendly alien named Cosmo, whose ship crashed near their town. Meanwhile, the villainous Dr. Doom plans to use an invisible bomb to ruin Christmas for the Norfins.

The magical trolls are in for a night full of ghosts and goblins as they enter the "Castle of Doom" on Halloween night.