I can't believe that I've finished the book (again) without quite figuring Frank out.

On what basis can he claim that he thought Emma must suspect something? Did he think Emma was kidding HIM about Mr Dixon?

And, would Frank have been less flirtatious with Emma if he thought she was becoming attached to him?

Mr K (!) picked up some clues, but Emma attributes Jane's behavior to an imagined relationship with Mr Dixon. (And, someone else pointed out that at least one clue was missed by Emma because she did not witness everything that Mr K saw.)