deRitter has lived on the edges of the underworld for many years. He is basically a small-time con artist who needs particularly gullible victims to be successful. For a reason even he can't understand, he returns to his home town with Leah, a prostitute, in tow. He has a fake emerald he hopes to make serious money with.
The story moves up and down the timeline. The reader sees deRitter as a boy growing up in a small, dull town--very much like the one that Madame Bovary despised--filled with and trouble. Off to war he went in his later teen years and after that he discovered how to beat the monotony of regular employment by working minor cons short and long.
In town again he sees old friends and old relatives; his strange relationship with his mother being the most disturbing. He also runs his con with the emerald and here the reader comes to see that he is not good at his work at all. And even when he scores he's unhappy. Which is where Leah the prostitute comes in.
She is plump--as he never forgets or forgives--she is ignorant in many ways and she is eager to get out of the town and back to what she consider civilization. But she also understands deRitter in ways he never understands himself.
He does not seem to know, for example, that he is afraid to let go of her. They have sex occasionally but their real bond is a version of the familial. More than girl friend she is mother/sister/consoler. And forgiver. She even manages to be amused about the occasional shame he feels for traveling with a prostitute. And she knows that the con he's running will lead to the tragedy that ends the short novel.
deRitter is a familiar figure in hardboiled crime fiction. The nickel-dime grifter that the real players use and toss away. Simenon turns the stereotype into a real human being. And his story into a bleak snapshot of self-unawareness and despair.