A woman is found murdered in her bathtub, and the murder made to look like a suicide. A strange symbol is found near the body. Then a second victim is discovered, who was also part of a group of tourists on a doomed expedition to Iceland ten years earlier. How are these deaths, and rumours of an Icelandic demon, linked to the secretive Association for the Study of the Writings of Maximilien Robespierre? And what does the mysterious symbol signify? The new Inspector Adamsberg novel.