 The feast of Hollebollegijs (which coincides with Christmas) is about to be celebrated at castle Bambergen, but the inhabitants are suffering from memory loss. Ambtenaar Ogterop Deux thinks somebody has been misusing a  Vergeetboek , a book in which you write down things you want to forget about. So, the Hamelaars travel to Wudel, where the nearest of those books is kept, and find themselves in the middle of a ghost party.