The article is a critique of Gunnar S. Paulsson’s book Secret City: The Hidden Jews of Warsaw, 1940–1945. After an in-depth analysis of the data and calculations contained in the book, Dreifuss accuses Paulsson of mistakes in his calculations regarding: (1) the number of Jews who survived on the “Aryan” side of Warsaw until the eve of the 1944 Polish Warsaw Uprising; (2) the total number of Jews who spent the war in hiding on the “Aryan” side and those among them who survived the Holocaust years; and (3) the (enormous!) number of Poles who acted to rescue Jews in occupied Warsaw. Paulsson’s calculations, which he made on the basis of erroneous statistical and methodological assumptions, led him to questionable historical conclusions, which should be rejected. Paulsson uses sources in a selective way as he quotes fragments which confirm his numerical estimates, at the same time ignoring other sources and often blaming the Jews for their own tragedy. He has also proved his unfamiliarity with both the available sources and the-then reality. The author dismisses Paulsson’s contribution to the debate on the number of Jews in hiding as worthless or even harmless as it invokes a language of allegedly fixed data.