Saw this on Talking Pictures channel (UK - old films and TV) who are running all 4 of this original Maigret series (BBC, early 60s). This episode was the first of series 3, and the supporting acting talent was clearly better than in some of the early shows!
Terence Alexander, Richard Vernon, and smooth Charles Gray all added weight to their roles, which in this one had an elderly ex-Diplomat murdered, when he would have been looking forward to marrying his true love, from the days of WW1, just free herself from an arranged marriage to link her family with another from the French aristocracy. The 2 had swapped love letters for many decades, latterly a letter every day!
Maigret, uncomfortable with this foreign world, used Lucas and even his wife to try and understand some of the letters. What role had the old chap's ancient housekeeper, hostile to everyone bar him and her priest, played in the mystery, if any? Who'd tidied up the 4 bullet casings?
An excellent episode, with a thoughtful ending, and a mention of what was then a new technique, testing the hands of people who might have a gun, as the discharge leaves residue behind.