Black threatens to take on b1, so White must create a stong threat. At the moment his queen is under-employed, doing nothing more than cover b4 and c5, a job which could equally well be performed by a bishop. How can white make use of the lateral powers of his queen?

Sometimes the solution to a problem cannot be deduced by a purely sequential reasoning process – a leap of the imagination is required. It seems likely that White’s queen will be involved, because at the moment she is not using her full powers, but how exactly? 1 Kd6! This certainly brings the queen into the game, because it creates the threat of 2 Qb7 mate, but otherwise it appears to be one of the most unlikely moves on the board. Not only does it allow Black’s king to flee to b4, it also permits Black’s rook to deliver check on either d3 or g6. However, both these checks block the h7-bishop’s attack on b1, allowing White to give mate by discovery 1…Rd3+ 2 Bd5 mate or 1…Rg6+ 2 Be6 mate. The only other move to meet the threat is 1…Kb4, but this leads to the third mate by discovery after 2 Kxc6.