Freemasonry was a source of deep fascination—and vicious persecution—for the Nazi Party during World War II. A deep suspicion of underground organizing and suspected Jewish collaboration led Nazis to round up scores of European Freemasons, seizing their belongings and sending many to die in concentration camps. Masonic lodges saw records and archives going back a century or more confiscated and used to identify suspected members. In the end, the Nazi Party had collected through plunder one of the greatest troves of Masonic records on earth.

On Sept. 8, Masonic researcher Helge Horrisland explores the plight of those WWII-era Masons and the Jewish prisoners forced to index and tend to what was, in effect, the largest Masonic library in the world—and, decades later, the efforts to repatriate those effects.