Well, first off, who really was Mr. Dussel? Mr. Dussel is actually Fritz Pfeffer, a Jewish dentist. Anne calls him Alfred Dussel because Dussel means nitwit in German and she didn't think too highly of him. Pfeffer (Dussel) was not Dutch, he was actually German and like the Frank family, was Jewish. He even had a Aryan girlfriend which by the Nuremberg Laws (not to be confused with the Nuremberg Trials) of Nazi Germany was completely illegal. So he too went into hiding because he was a Jew and if caught he would be sent to a concentration camp. Eventually when the members of the Annex were captured, he was sent to a concentration camp and he died there. I don't recall reading that he was Dutch in the diary...but it's been a while since I read it. However, the real man, Fritz Pfeffer was German.