Freemasonry is a centuries-old social network with a distinctive ritual tradition. During the Second World War, the Nazi regime directed its enemy image and propaganda against the lodges, portraying them as part of a “Jewish conspiracy”. In reality, tolerant Freemasonry represented a potential source of resistance and therefore a threat.In September 1940 the occupying authorities banned Freemasonry and robbed all Dutch lodges of their possessions and heritage. The principal target was the Freemasonry Museum in The Hague, with its famous Kloss collection and the legacy of Prince Frederik. Members took great risks to save what they could. After liberation, legal restoration proved difficult, with the burden of proof placed on the victims. Many valuable regalia and ritual objects remain missing. Based on archival research in the Freemasonry Museum, this publication maps this little-known aspect of wartime history for the first time and provides new leads for provenance research.