I shall make a point , of reading that Holmes Story again, Hunters Lodge, Davenheim and Clapham Cook are my 3 favourite Poirot Short Stories.
Getting back to "Evil under the sun" - the Ustinov movie, they did something that I felt made the story tighter and better for a movie - MOVIE SPOILER - they changed the characters to have a connection to the victim. The Gardeners are not just american tourists but producers who expected Arlena to be in their next project, while she reneged on her contract, causing them a loss; instead of the (suspectedly unbalanced) reverend, there is the effeminate scandal writer who Arlena is threatening to sue if he publishes his book about her; Blatt is after Arlena because she stole a jewel from him. That makes for a lot of credible suspects. I was rather sorry they eliminated Rosamund, but replacing her with an Irene Castle - an old flame of Marshal, kind, spicy and an old rival of Arlena - was brilliant! So, movie-wise - this is still my favorite.