On the outskirts of Paris, 2 men have been found with their throats cut. It is assumed that this is a drug-related incident of the kind so often uncovered in that area of town. But Adamsberg is convinced that there is more to it. The trail also leads Adamsberg to a cemetery, where a grave has been disturbed with no apparent motive.
Commissaire Adamsberg leaves Paris for a conference in London. Accompanying him are Estalere, a young sergeant, and Commandant Danglard, who is terrified at the idea of travelling beneath the Channel. It is a welcome change of scenery, until a macabre and brutal case comes to the attention of their colleague Radstock from New Scotland Yard.
When strange blue chalk circles start appearing overnight on the pavements of Paris, the press take up the story with amusement and psychiatrists trot out their theories. Jean-Baptiste Adamsberg, a policeman is alone in thinking that this is not a game and far from amusing.
JOINT-WINNER OF THE CWA INTERNATIONAL DAGGER AND EURO CRIME''S FAVOURITE READ OF 2013 ''People will die,'' says the panic-stricken woman outside police headquarters. She has been standing in blazing sunshine for more than an hour, and refuses to speak to anyone besides Commissaire Adamsberg. Her daughter has seen a vision: ghostly horsemen who target the most nefarious characters in Normandy. Since the middle ages there have been stories of murderers, rapists, those with serious crimes on their conscience, meeting a grizzly end following a visitation by the riders. Soon after the young woman''s vision a notoriously cruel man disappears, and the local police dismiss the matter as superstition. Although the case is far outside his jurisdiction, Adamsberg agrees to investigate the strange happenings in a village terrorised by wild rumours and ancient feuds.