When Commissioner Vaimber gives his colleague and cousin Maigret the case of the pharmacist's wife, he doesn't really know what to make of her. Agitated, on the run with her children, she claims to have seen the corpse of a young woman in her basement, apparently assassinated by her husband! Upon reading the sketchy deposition, Maigret touches upon a few facts that could be true. But what should he believe? A real murder? Who is the perpetrator of the crime? He or she? And where is the husband now, disappeared at the same moment as the corpse that was never found. Maigret sees only one solution to elucidate the mystery: go incognito, under the assumed identity of a salesman, to the boarding house where the pharmacist's wife and her children have taken refuge, to watch her every move in the hope of finding contradictory behavior... And so he does. Arriving under the pseudonym of Jules Fontaine, Maigret remains in the company of Mrs. Four: (She is called Mrs. Four because she occupies Room 4 at the boarding house.) He discovers therein the micro-society of this establishment on the outskirts of town... Day after day, Maigret slyly takes advantage of the help offered by the personnel and the occupants of the establishment as he retraces the steps of the murderer. A murderer who is crouching nearby in the shadows, ready to pounce on the prey who committed the error of being witness to his last murder... Directed by Philippe Berenger, 1991, color. In French with English subtitles.