This is the fifth book is about the Prussian family. The father is trying to take care of his wife, who is addicted to the drugs of the ninteenth century, a time when addiction hasn't been identified. There is only one place in the world trying to treat people for drugs, Vienna. So Otto has to take his family there and cope with the Viennese way of seeing and doing things. Will Hildegard overcome her dependencies? How will Otto cope with the strange life? How long will it take?
