Saw this on Talking Pictures channel (UK - old films and TV) who are running all 4 of the original Maigret series (BBC, early 60s). In this one, he's taken his wife back to his birthplace, but in Church the Countess, who he'd revered when he was a boy, collapses and dies. She was quite old, and had already had a heart attack, but was she helped to die?
Maigret doesn't involve his team at all, but probes all the relevant locals, priest, doctor, the landagent who runs the estate, the young 'assistant' to the Countess (or could he be more?!), and her spendthrift son appears, who'd been looking for yet another handout, to avoid going to jail. But it seems there is very little money left, with no shortage of possible culprits who've been helping themselves.
Some excellent acting talent, Wiliams Mervyn & Franklyn, Philip Stone, and Colin Jeavons, who between them would appear in hundreds of dramas and comedy shows over the years, help move this episode along, though I note that a few details got changed when they did the same story for the Gambon Maigret series.
A Choirboy provides a key clue, and we learn what had shocked the Countess into a fatal heart attack.