Concerning Dame Ngaio Marsh

 Recently a close friend forwarded this review to me:

Every Roderick Alleyn Novel (Fiction, Ngaio Marsh, 1934-1982) Roderick Alleyn, the Shakespeare-quoting, handsome, aristocratic Chief Inspector of Scotland Yard, spans the gap between Sayers’ Lord Peter Wimsey and P.D. James’ Adam Dalgleish. Not as inventive (in plot or dialogue) as Sayers, and not as deep (in character and psychology) as James, Marsh still easily beats Christie for human stories, and her puzzles are reliably honest legerdemain, the best kind. The early novels have a Sayers-Wodehouse sort of air, and she never approaches the psychological starkness of late Allingham, but at her best (Surfeit of Lampreys, Scales of Justice, and the near folk-horror of Dead Water, all Recommended) she combines knowing lightness, humanity, and cruelty better than most mystery writers. Many Alleyn novels have a theatrical setting, combining two hothouse genres with general success. –KH

Now, I am well known as a swooning devotee of the traditional whodunit mystery, featuring puzzles and clues and stuff. There are very few practitioners of the art nowadays, although I would be remiss not to cite the inimitable Steve Hockensmith and the always-excellent Aaron and Charlotte Elkins. (Although, come to think of it, I myself have imitated Hockensmith, so maybe he's only mostly inimitable.) I'm always searching for new authors in the classic mold. So nothing would please me more, at least within the confines of the literary universe, than to find that I'd unjustly overlooked Ngaio Marsh.

The thing is, I've never thought much of her. Her writing style is good, but her plotting always struck me as pedestrian at best. On the other hand, my wife likes her, and brought a dozen Marshes to our library. So I resolved to try again. I picked out one of the books I hadn't read, Death in Ecstasy.

Here's what happens:

1. A woman is poisoned while attending a peculiar religious service.
   
2. Ordinary police work reveals that she had a serious quarrel with someone, regarding the theft of some bonds which she had given to the sect. 
3. It's not clear with whom she quarreled, but it's presumed that that's who killed her.
   
4. One of the suspects actually overheard the quarrel, but he won't tell the police who the other party was.
5. Except that, a couple chapters later, he does tell them who it was, and that's your murderer.
6. The end.

There are a lot of melodramatic trappings, but that's it. That's the mystery.

Ngaio Marsh fans, please tell me: what am I missing?