Robert Joe (RJ), an urban explorer and Historian Dr Sam Willis are on a mission to uncover the secrets behind Heinrich Himmlers Wewelsburg Castle in Germany. On March 31, 1945, Himmler had ordered a member of his staff on a suicide mission to blow the castle up before it fell into American hands as US troops closed in on it, but Himmlers staff was not equipped with enough dynamite to successfully destroy the castle. It survived. When the American troops reached the castle two days later, they found a room with a strange symbol now called the Black Sun and a crypt below it with pipes connected to centre of the room believed to be for an eternal flame. The mystery shrouding the castle has given birth to bizarre pop culture fantasies from comics illustrating Himmler summoning a demon in the crypt to video games portraying Himmler as a master of the occult, with Wewelsburg castle at the centre of it all. RJ and Sam embark on a journey to discover the origins of these speculations and the truth behind the rumours. They meet various experts - a Scientific Assistant at Wewelsburg District Museum, who interviewed SS commando, Heinz Macher, about his failed attempt at blowing up the castle; the museums director who reveals the secrets of the SS Honour Rings; a researcher who once interviewed an SS officer who was stationed at the castle. As RJ and Sam fill in the blanks of this mystery, they visit other sites that Himmler was linked to the Externsteine, a rock formation that best depicts Himmlers desperation for a Germanic history; Heidelberg Thingstätte, one of many outdoor amphitheatres built by the Nazis for propaganda, and the Bundesarchiv, a throve of documents and pictures that reveal the depths of Himmlers mind.