Retrograde Chess Puzzle - Solution

(Step 1, of 3)

                   
8  
7  
6  
5  
4  
3  
2  
1  
  a b c d e f g h  


Raymond Smullyan

WHITE TO MATE IN ONE MOVE  © Raymond Smullyan

1. It's White's move, so the Black King is not in check.
Conclusion: The Black King does not stand on d8.