This time we have a White queen and rook directed at g7—but with a White bishop in front of them creating the kernel of a discovery. What to do with the bishop? Use it to block the path of the Black queen that defends the mating square. Hence White plays Bf7+. If Black replies BxB, White mates with Qxg7#. Black is better off sacrificing his queen with QxB, leading to RxQ for White. This avoids immediate mate, though it leaves White with a decisive material advantage and an eventual forced mate anyway with careful play.