Jean-Baptiste Adamsberg is not like other policemen. His methods appear unorthodox in the extreme: he doesn't search for clues; he ignores obvious suspects and arrests people with cast-iron alibis; he appears permanently distracted. In spite of all this his colleagues are forced to admit that he is highly successful — a born cop. 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. Adamsberg is alone in thinking this is not a game and far from amusing. He insists on being kept informed of new circles and the increasingly bizarre objects which they contain: a pigeon's foot, four cigarette lighters, a badge proclaiming 'I Love Elvis', a hat, a doll's head. Adamsberg senses the cruelty that lies behind these seemingly random occurrences. Soon a circle with decidedly less banal contents is discovered: the body of a woman with her throat savagely cut. Adamsberg knows that other murders will follow. The Chalk Circle Man is the first book featuring Jean-Baptiste Adamsberg, one of the most engaging characters in contemporary detective fiction.

People will die, says the panic-stricken woman outside police headquarters. She 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 grisly end following a visitation by the riders. Soon after the young woman's vision a notoriously vicious and cruel man disappears. 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.