At a small, outlying suburb of Paris that seems to be three houses, a butcher shop and a garage or two, a corpse is found in a car. It's a Jewish diamond merchant from the Low Countries. The police are soon sweating the owner of the garage, George Koudria. He is an exiled Swedish aristocrat who lives in one of the houses with his sister, Winna Winnifred. Enter Inspector Maigret in the person of Pierre Renoir, the brother of the movie's director, Jean Renoir. Koudria does not crack, and he is sent back to his home. He flees across the border, while Maigret wanders around, asking question that have nothing to do with the events, watching and listening.
Renoir (the director) made this film between LA CHIENNE and BOUDU SAVED FROM DROWNING. Those films would seem more typical of his movies, with this one an odd outlier, a potboiler to offer some income and prove he is a bankable film maker. I found it fairly typical of his works in which relationships are unclear and it is up to Renoir (the actor) to winkle them out for the audience. You may look on it as a try-out for THE RULES OF THE GAME with murder, and Simenon's name to add to the commercial value of the effort. It's a fine, atmospheric movie, if you ignore the simple matter of the mystery.
The problem I have with the mystery is that there is a perfectly good and simple explanation of who did it up to the point where Maigret begins to demonstrate his theory. Simenon and the Renoir brothers play fairly with the audience in this murder mystery, but the actual solution is far more complicated than the one offered early on. That the solution turns out to be the truth is a trick of the writer. Another solution could just as easily been written and Maigret could have produced the evidence equally easily, should Simenon and the director have wished it. In effect, they produce the clues after the audience has been given the complete story.