A hunt for ghosts between demons and strange legends. From Iceland Iceland to the French Revolution. The new case for Commissioner Adamsberg and the most extravagant Army of Parisian anti-drug. All the anti-crime of the thirteenth arrondissement of Paris is mobilized on the case of the two apparent suicides. The very high captain Danglard, great admirer of white wine, the energetic Violette Retancourt, the specialist in freshwater fish Voisenet. But above all the unanswered, irresistible "sheet of clouds", Commissioner Jean-Baptiste Adamsberg. It all starts with the discovery of two bodies and the discovery of a strange symbol scribbled next to each of them. But as always happens in the stories of Fred Vargas, this is not that the start of an adventure that will end up entering halfway between a Balzana sect of adepts of the French Revolution and a trip to Iceland ended in tragedy.