Strange events are happening in Paris: almost every night, circles drawn in blue chalk appear here and there. Each of them contains some old thing, found in a garbage container or picked up right on the sidewalk. Parisians consider this a bad joke or the prank of a harmless madman. No one except Commissioner Adamsberg thinks things could take a bad turn. And suddenly one night in the next circle they find the body of a brutally murdered woman. However, the story does not end there...