Thanks, I always look at these, although they are far too tough for me....
Deductive Puzzle #51
vj1: The c8-bishop should be on b7. Back to the ol' drawing board!
You can triangulate with white's queen to get to the right position e.g. 19.Qe2, Bb7 20.Qe1 Bc8 21.Qd1 Bb7
Ah, so now the position is slightly different.
Can we go back to the ol' drawing board now? Pretty please?
Without looking at the answer yet, I would assume it captured Black's e-pawn, and the pawn on the e-file now is the g pawn.
Edit: Nm... I just counted captures and that makes no sense.
Maybe black promoted their g pawn on the e file to a knight and that knight was captured on b4?
Black had to promote their g-pawn on e1, and it had to be a rook. A knight simply couldn't have escaped (where did it go? anywhere would either take a pawn or check the king on e2). Therefore a black rook was taken on b3 or b4, and since the a8 rook couldn't have escaped, it must be the h8 rook that started its life as the g-pawn. Furthermore, in order for this promoted pawn to get back to h8, it needed to use the a-file, so the a1 rook must have moved to get out of its way (along with the queen). Thus, the h1 and a8 rooks are the two that haven't moved.
Great puzzle, great series of puzzles.
Youre welcome.
I need to figure out how to go about posting the next series of puzzles. "The Chess Mysteries of Sherlock Holmes" will be coming shortly. Would people prefer I boil them down to the puzzle alone as I did for these, or for me to post the problems as the stories they are written into?
Either way would be interesting. I think I'll stay away from solving them, except to maybe drop a hint or two along the way. It wouldn't exactly be fair as I have the book. When I get a chance, I'll be getting this other book that you've been using up to now, I just haven't had the money/opportunity to do so.

Which two of the four castles have never moved in this game?
Know that the Black king has never moved, and the White king has moved only once.
It saddens me to be at the end of the book!!! Again, to remind you all, these puzzles come from "The Chess Mysteries of the Arabian Knights. "If you enjoyed these, I highly suggest other collections by Raymond Smullyan.
This isn't really the end though, I have unorthodox puzzle collections which I will begin posting in due time.