Black’s queen and rook are on the same rank as his king. At first a pin seems nowhere in sight; it would have to be imposed by White's own rook or queen, and neither can reach the seventh rank. The trick is to look through the obstacles: White has his rooks doubled on the same file as Black’s rook on d7; if the pawn on d6 weren’t in the way, White could play RxR, pinning and then winning Black’s queen. The question is how to get the pawn off of its file. Do it the usual way: take something the pawn protects. The only thing it guards here is the knight on e5, so White plays QxN—a costly sacrifice, but one that pays off. Black replies d6xQ. Now the obstruction to the pin has been removed, allowing White to play RxR and then win the queen. The rear rook provides the needed cover for the forward one. White nets a piece with the sequence.