Ellen Lucas comes across another missing person in Kastell: the father of the family, Oliver Haffner, has been missing for days. With the help of the resident Father Eurasius and the doctor Dr. Gohar Ardeshir Lucas succeeds in clarifying the identity of the unknown. Her name is Jeannette Wilson. She worked as a teacher in Kastell. What was her relationship to Oliver Haffner? Was she actually sexually abused by him, as the women from the nature center claim? Haffner's family is convinced of his innocence and suspects Anna Stern of having eliminated him. Supposedly, behind the nature center is a circle that practices unlawful, occult activities. Haffner had proof of this and wanted to expose the group. Ellen Lucas falls under the spell of Kastell.
What is it about the ancient lakeside sacrificial site, and why is it feeling weaker by the day? Inspector Lucas senses that Anna Stern is the key to solving this mysterious case.