A variation on the same theme. Again White attacks nothing and again he looks for any checks he can give, perhaps noticing this time that the knight on f6 is loose. His possible checks are two: Qe8, which loses the queen right away to Black’s knight or rook; and Qe6, which is far more interesting because it is safe and forces the king to move. Naturally Black will want to move the king in a way that allows it to protect his knight, which White is poised to capture; so Black tries Kg7. But now we are back in the familiar position where an enemy piece is guarded by its king. What to do? Give another check. White plays Qe7+, and now the king is forced to the back rank or to h6. Either way, White takes the knight next move.

There are two points to take away here. One is that the same piece may be able to both give check and take a piece that the king protects once the king moves. The other is that sometimes more than one check is necessary to create the needed arrangement.