White’s best move obviously is the free QxN. Or is it? This is a sterling example of the importance of looking beyond a good move to make sure there isn’t a better one. Do it in the usual way: look for loose enemy pieces, checks, and mate threats. Black’s rook is loose; follow this observation by looking for a line the queen could use to attack it while also being aimed at the king. Qh4 suggests itself. The move seems to fail because the h6 pawn blocks your queen’s path to the Black king’s position. But there is more than one way for a fork to “work”; if the move doesn’t give check, it still is enough if it threatens mate. Examine the Black king’s position and you see that White’s rook on the open g-file has the king trapped on the side of the board, and you see as well that the king has no defenders. The conclusion: Qxh6 would be mate. So after White’s 1. Qh4, Black doesn't dare move his rook; he has to let it go. (Then again, no matter what Black does, White can force mate soon enough anyway. If Black plays 1. ...Kh7, for example, then White plays QxR and can't be stopped from playing Qg8#; Black can only delay the move with useless gestures like Ne8 or Qxb3+.)