Despite writing detective fiction, I've noticed that Christie seems to want to at least play fair with the police, and not make them all out to be Total Idiots.
And I like the fact that the concept of karma is cropping up here... but Clithering is still a bit more laissez-faire in that sense than I'd like to see in a top police type guy! Yes, it still matters if crimes (I mean, at least if we're talking about things like murder and other "big" crimes) go unnoticed and unpunished by society! I do however like that he realizes how important innocence can be, or at least not pointing guilt at those who you're not sure are guilty!
There's not too much to say about the story itself - it's nice enough, but not my very favorite of the collection. I think partly because it seems the flower thing just muddies it further - if you have the names spelling out "Death" in the letter, why bring dahlias and flower catalogues into it at all?
Edit: Oh, and I almost forgot to add that I found it amusing that in this case, the *one* person who wasn't "hired help" in some form turns out to be the culprit. :)
The Schwartze Hand - This would be The Black Hand, translated, and there is this society, but that doesn't seem to be quite the same thing. I suspect this exact society was made up or at least only loosely based on real societies, since one of the foci of the story was instrumental in breaking it up.
The Camorra - This is an Italian mafia-like organization.
Elevenses - I like this term. :) It's sort of a "second breakfast" a la Hobbits. Or more accurately, like afternoon tea, but in the morning between breakfast and lunch.