The crime novel takes place in the second half of the 19th century. Dr. Bern arrives at a hospital for the mentally ill, a sinister castle, the assistant position of the director. The castle and its inhabitants are burdened with a dark past, which only gradually becomes apparent to him, in which he has to prevail against the resistance of forging colleagues and the director. The sole daughter of the director was the victim of an insane serial killer 23 years ago. Bern visits him and gets an insight into the fate of the murderer. Bern has doubts whether the alleged murderer is really rightfully locked in a dungeon for 23 years and goes on the dangerous search for the truth.