Autumn has arrived - but this year Petronella has no time to help with the apple harvest. She is flying to the witches' swamps to attend a large gathering. All witches who have been awarded the golden witch braid are invited. What an honor! Lea and Luis are also going on a trip - they are heading out for a school excursion. It soon becomes clear that the castle where they are staying is haunted! When a few rather unfriendly ghosts lure the twins and their friends into a trap, things get tense. But fortunately, it's not far from the witches' swamps to the haunted castle. And so Petronella can rush to their aid just in time...