JA Topf and Sons began as an unremarkable provincial engineering company, but under the direction of Ludwig and Ernst Wolfgang Topf, it began to manufacture cremation ovens for Auschwitz and Buchenwald. Drawing on interviews and thousands of archive documents, this investigation reveals how the brothers and their colleagues, driven not by ideology but by personal ambition, facilitated the murder of millions, and tells the story of a descendant who sought to expose and atone for his family’s crimes.