Again we have a familiar pattern with a new wrinkle. White sees that adding his queen’s weight to the pressure his bishop already imposes on g7 would threaten mate. It also would attack the bishop at d6, which now is attacked once and defended once by rooks from each side. But simply playing Qd4 would be a mistake. You have to think out the resulting series of exchanges to make sure it works. After White plays QxB, Black recaptures with RxQ; then White answers with RxR—and has lost his queen for a bishop and rook! You have to attend to the values of the pieces involved. This pattern worked in the previous frame because Black would have had to sacrifice his own queen in the recapturing process, but that’s not so here. All this means, however, is that the bishop is an unsuitable target; it remains to be considered whether an exchange would improve it. What if White starts by playing RxB? Then Black replies with RxR. Now Qe5 safely threatens both mate and the rook, netting a piece.