Cormoran Strike visits his family in Cornwall. There, a private detective, once again on the headlines after he caught the Shacklewell Ripper and solved the murder of Culture Secretary Jasper Chiswell, is approached by a strange woman and asked to find her mother, who disappeared under mysterious circumstances in 1974. Strike had never had the opportunity to investigate a hanger, especially one that was forty years old; the chances of success are almost zero. But he is intrigued by the mysterious disappearance of the young doctor Margot Bamborough and takes on a case that turns out to be perhaps the most puzzling in his practice.

With his faithful assistant Robin Ellacott, who has managed to become a full partner in their agency, Strike is looking for the elusive eyewitnesses and interviews unreliable witnesses, seeks approaches to a maniac-murderer who has been behind bars for four decades, with disgust masters fortune telling with Tarot cards and astrological wisdom - and gradually becomes convinced that even cases so old can be mortally dangerous...