And Then There Were 30: The Hollow by Agatha Christie

Well, whenever we go beyond an hour of nattering away about a
title, it's a good sign, and this episode is no exception. Come and
bask with us in the many splendors of The Hollow, a much-beloved,
mid-career masterwork of Christie's with rich characters and yet
almost no puzzling to speak of, despite the presence of our dear
Poirot. If this one is a Christie "crown jewel," it's one with all
sorts of imperfections, but everyone knows it's the flaws that make
a thing more interesting....