Mr. Dussel arrives and is shocked to discover the Franks. He had completely been taken in by the story that they had escaped.
The van Daans give him a copy of the "Prospectus and Guide to the Secret Annex," which demonstrates that the van Daans do have a sense of humor after all. It’s written like a typical tourist tract and describes the hiding place as if it is a luxury resort for Jews. You should definitely check this part out, if you haven’t already.