Signed, Picpus by Georges Simenon
Maigret dismantles an intricate network of lies stretching from Paris to Nice in book twenty-three of the new Penguin Maigret series.
“Mechanically, he had put his pince-nez down on the blotter and looked at it there with his large, short-sighted eyes. It is at that moment that the strange thing happens. One of the lenses, acting as a mirror, reflected the criss-cross, hatched ink marks which had dried on the blotter and he could just make out a couple of words.”
When a fortuneteller is found murdered in her apartment, Maigret must find out not only who commited the crime, but why it was predicted in a note found earlier–signed by the unknown Picpus.