Just picked up the new book at the library (yay!), and want to refresh my memory.

Does Harvey know?  I seem to recall that it really looked like they were going to have to tell him in the last book, but I can't remember if they ended up keeping the secret or not.   It seems like they told someone recently (last book or two) and I just can't remember who it was.

I know Aaron, Dennis and Brenda (?) know, but who else?

I just finished Dead Man's Puzzle and, no, Harvey doesn't "know".  Not everything anyway.

SPOILER SPACE

He knows Cora can't solve puzzles, but he hasn't realized or been told that she doesn't make them up either.