What on earth is she thinking of?
But perhaps the most interesting example of a mainstream novel which is also a detective story is the brilliantly structured Emma by Jane Austen. Here the secret which is the mainspring of the action is the unrecognised relationships between the limited number of characters. The story is confined to a closed society in a rural setting, which was to become common in detective fiction, and Jane Austen deceives us with cleverly constructed clues (eight immediately come to mind) — some based on action, some on apparently innocuous conversations, some in her authorial voice. At the end when all becomes plain and the characters are at last united with their right partners, we wonder how we could have been so deceived.
— P.D. James, Talking About Detective Fiction, pp 6-7.
It makes one — well, me — think of “The Macbeth Murder Mystery.” “I’m going to buy a copy of Hamlet, and solve that.”