1414. The whole of Aachen is in an uproar: the new choir hall of the cathedral is to be inaugurated on the anniversary of Charlemagne's death. In the run-up to the event, a series of mysterious murders overshadows the big event. A quick investigation is necessary to ensure that the guests do not stay away. The relic dealer Marysa picks up the trail of the culprit. Her realisation that the murders are linked to the keystone of the choir dome - the "Christ Stone" - puts her life in danger...
