How is it possible, for those who were not “under that sky of blood”, to speak about the Shoah without outraging again, even involuntarily, millions of victims?What are we speaking of, when we mention the Shoah? Starting from these two questions, the paper approaches Treblinka, the biggest factory of “pure” death set up by the Aktion Reinhard, with the purpose of understanding, through the words of Yitzhak Arad, a survivor who became a historian, and those of other witnesses, dead or alive, interviewed by Claude Lanzmann, the reality of the concentration camps.