>>>i see what you're saying Buenchico but it isn't a story by Agatha Christie
Buenchico bangs his head on the desk and asks himself why he's always assumed that AC wrote it! It must be something about the style of the writing, although I admit that I've never read the original novel. ('The Wheel Spins' by Ethel Lina White - Thank you, Wikipedia!).
My point holds true, I think, though. Mystery novels from that period tend to work best on screen when there's a bit of humour injected into them.