Saw this on Talking Pictures channel (UK - old films and TV) who are running all 4 of the original Maigret series (BBC, early 60s). As others have said, this was a cracking episode, featuring a dominant performance from Lana Morris, who was in a lots of the show. She'd been on TV a lot by then, made many later appearances on many shows, AND was much in demand in the West End. By the time of this 3rd series with Davies in the lead role, the supporting acting talent had risen quite a way from some of the early shows!
One of those reviews was by 'Sir-Oblong-Fizzolongs' and this is a disturbing trend, twice in just a few weeks he's made an accurate comment!
Despite the lead role ('Felicie') having many irritating qualities, and indeed spending time and effort concealing evidence from Maigret (in case her young man was at fault), the detective does warm to her - as he has done a few times with potential or actual criminals.
And gradually the truth comes out, why the actual killer might have been in the house, and setting a trap for his return. This same story was covered in the Micheal Gambon series as Maigret (2 runs of 6 shows), and was very similar although the Gambon versions had a longer running time. One shortened detail in this one involved a gross coincidence, to facilitate the discovery of the murder weapon, which is the only reason I've dropped this one's rating to a 9 out of 10.