Examine Black's checks. The most conspicuous are the two with his rook: Rg1 and Rf4. Rg1 doesn't seem too good; it allows White to play his threatened KxB. Rf4 almost seems to work, as the rook takes protection from the pawn on e5 and the White king turns out to have no flight squares. Alas, f4 is guarded by White’s queen and knight. But when the only obstacle to a mating move is defense of the needed square by other enemy pieces, turn your attention to the removal of those pieces. Black sees a capture available in 1. QxN+ and so experiments with it; it calls for the recapture QxQ—and now both of the guardians of f4 have been eliminated, permitting Rf4#. It might seem that if White is attentive he therefore will not play the recapture QxQ after all, but then Black mates in a few moves anyway; for if White keeps his queen where it is to prevent Rf4#, he loses it to QxQ next move.

The position is, of course, yet another study in a theme seen earlier in the chapter: the capture of one guard that incidentally removes another as well.