Just saw this (again) as I'd seen the Rupert Davies Maigret back when they first got shown. Now they're on the UK Talking Pictures channel (old films and TV).
This episode wasn't quite as good as some, a couple of the side characters were guilty of some really 'ham' acting, maybe there wasn't time for the director to coach them better? But the sets are improving, and quite a bit of outside film in this one -- though the lack of traffic in 60s Paris always seems odd?!
I use the Christie term in the title as the main character (the murder victim) was disliked by just about everyone, so quite a few feasible motives. He'd gone to see Maigret, claiming there was a plot to kill him, and mentioned they'd been to school together --- Maigret didn't recall him at first, but when he did -- hadn't liked him then either! Oh, and one for trivia fans, the actor playing that Butcher was the voice of a Bond villain, Blofeld!
Maigret gradually wotks out what happened, by skilful questioning, but the last few minutes were (IMO) quite odd. Having discovered the murderer has 'done a bunk', he and 2 of his team take a car and drive right out to Brittany to a spot (near Maigret's birthplace) where he's sure the guy will be hiding. That's a VERY long way, they seem to make the trip very quickly (empty roads helps!), and get their man. Very dramatic, BUT - in the real world, they'd just ask the local police to round him up!