Strange things happen in Paris: almost every night, in one place or another, blue chalk circles appear. In each of them lies something old—a trinket found in a trash container or picked up right on the sidewalk. Parisians think it’s a bad joke or the prank of a harmless madman. No one except Commissioner Adamsberg believes the case can take a nasty turn. And then, one night, in yet another circle, they find the body of a woman savagely murdered. But the story doesn’t end there…