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 the other 2 reviews (so far, Mulkern & Fisher) have said, this was a lively episode, with several twists and turns.
Lapointe hears a shot when on his way home, having had a drink or two, from his sister's engagement party. He tries to investigate, but gets humiliated by the nouveau-riche people in the big house, and has to write a suitable report for Maigret.
Maigret is wary of the wealthy family's connections, but lets Lapointe try to follow up their only lead, a distinctive car, with a driver who'd fled the scene. Soon a body turns up, and Lapointe and the team start to place some of the murder jigsaw pieces on the board.
The car driver - a friend of the deceased - is soon traced, but Lapointe gets imprisoned. Maigret goes to see the wealthy businessman with lofty connections, and wonders why his sister has rushed off for an American holiday. Smelling at least one rat, he gets the team to start closing the net, and Lapointe turns up with a big clue.
John Carson made an excellent villain, Terence Alexander (also in zillions of subsequent shows) is the victim (but a real casanova), and there's a small part for the thug from the Ladykillers, a terrific 50s film with Guinness and Sellers.
There's a comedy fight scene in a garage, Lapointe goes to Hospital, and Maigret gets an admission from the villain -- with a surprise twist at the end. Despite a couple of holes in the plot (where did the shot happen, and other evidence that the principals are lying), a great episode - as the others have said!
And I've now seen this one again, Talking Pics are re-running all the BBC Maigrets, AND showing the Cremer (French) ones. I'm not sure the ending stood up legally, as they could have surely charged the family with not reporting a death, and depositing the victim's body on a suburban street. Plus they knew the shot came from upstairs, not the ground floor as the family claimed. Maybe they just did not have the running time to really tidy up the loose ends?!