http://www.futilitycloset.com/2008/03/23/king-queen-knave/
King, Queen, Knave
Vladimir Nabokov composed chess problems. Here's a clever one from 1932: "White retracts its last move and mates in one."
This is an instance of retrograde analysis: Of the many legal moves that White might just have made, only one can be revised to yield an immediate mate. Can you find it?