Absolute spoiler. Look at all those covers. The one in our library has a library binding. May be part of Simenon project. I am pretty sure I read this before. A prominent wine merchant is shot in the street as he is leaving a house of ill repute which both provides facilities for illicit couples and women for partnerless men. This guy is there with his secretary. He is a compulsive womanizer (huh) and a real bastard to everybody. Maigret wanders around, with the cold or the flu, talking to people who don't tell him much. The wife who put up with the guy is given significant descriptive treatment. Maigret is contacted by a man who wants him to know how bad the murder victim was and who turns out to be the murderer. He comes to confess to Maigret at home in the middle of the night.

I read this with Maigret and the Man on the Bench and they share the important plot point of a man who loses his job and doesn't tell his horrible wife but pretends to keep working & somehow brings home money. There are differences (of course) but it is a theme.