The mystery of the largest freely swinging medieval bell in the world. During construction work under the Erfurt Cathedral Hill, a hidden grotto is discovered. Twelve mummies in centuries-old robes sit around a stone tablet, each bearing a mysterious symbol: a bell from which a snake winds. And there is something else that is extremely puzzling: one of the corpses is only a few years old. Historian Jonas Wiesenburg is hired as a specialist consultant by the LKA. He has no idea that he is about to uncover a dangerous secret surrounding the famous bell Gloriosa and a sinister plan for revenge.