How to Write a Mysterious Mystery?

I write about five thousand words a day, and i use 20 minute timees to keep me rearily focused. I start with the setting and what the end results going to be. Two or three books recently, i've had to change because all these great ideas i came up with when i was sitting down to write murder misteries for the samefor the first time, im running out of them. And it's hard to be original. Am sure that lots of people have written all y my twists before, but i've never sat down with agatha christia and said, ok, i'm going to do the, you know, death on the nile twist. It is