It is Black's move in the game Varavin-Terekhin, Perm 1998. His kingside is under some pressure from White's active pieces, all of which are in play. On the other hand it is not clear that White can land a decisive blow just yet. On top of that Black is a pawn up and can annoy White with moves like ...Rb8 and ...c6.
Black's next move was 1...Qb8? He had probably decided that White was threatening the manoeuvre 2.Qg4-h4 and so he rushed to meet it with a manoeuvre of his own: 2...Qxb2-c1#. But sending the queen away from the kingside should have set a few alarm bells ringing because it temporarily gives White a huge preponderance of force in that sector.
Varavin didn't need any more encouragement than this. He plunged ahead with 2.Qh5!? and left his opponent to think it over. Taking the queen would lose immediately (2...gxh5? 3.Nf6+ Kh8 4.Rxh5+ Bh6 5.Rxh6#) so Black was forced to play 2...Rd8. Now White opened up some lines with 3.Rxg6 fxg6 4.Qxg6.
Black is a rook ahead but has a difficult decision to make. If he tries 4...Qb6 then White mates with 5.Rh8+! Kxh8 6.Nf6! Nf3+ 7.Kf1 Ng5 8.Qh5+, etc. That leaves only two choices: should Black put his bishop in play with the unpinning move 4...Kf8 or should he start a counterattack against White's king with 4...Qxb2? He chose the queen move to which Varavin found the cool reply 5.Kf1! This not only avoids the threatened mate but also cuts out ...Nf3+ as a defence to White's attacking move Ng5.
The game continued 5...Qc1+ 6.Kg2 Qf4 7.Rh7! Qf3+ 8.Kg1 Qf7 and now Varavin settled matters with 9.Rh8+! Kxh8 10.Qxf7. Black had to resign a few moves later.
When I first looked at this game I wasn't impressed with White's combination. Let's peel back to the position after 4.Qxg6 and try the alternative defence 4...Kf8. In Informant 75 Varavin dismisses the king move with the variation 5.Ng5 Nf3+ 6.Nxf3 and makes no further comment. But then how does White deal with 6...Rd6? I can't see a clear way forward; for example, 7.Qf5+ Rf6 8.Qxe5 is met by 8...Qe8 and now if 9.Be2 then 9...Rxf3!? 10.Rh8+ Bxh8 11.Qxh8+ Ke7 12.Qxe8+ Rxe8 13.Bxf3 Rb8! and Black has an easily won ending.
Instead of 5.Ng5 White can also play 5.Rh7. This looks more promising but Black can set up a solid defensive line with 5...Rd7. After 6.Qh5 White has reached maximum activity but the further tactic 7.Rh8+ leads only to perpetual check.
The conclusion is that White's attack after 1.Qh5!? is only good enough for a draw.
Time to bring in the heavy artillery. I gave the position after 1...Qb8 to Toga II, one of the stronger chess playing programs available. Instead of playing 1.Qh5 it wasted no time knocking Black to the canvas with 2.Nf6+!! Bxf6 3.Qh5! Deflecting the bishop away from g7 is worth a whole piece because it sets up two crushing threats. Of course the first one is 4.Qh7#. The second one is revealed after 3...Re8 4.Rxg6+ fxg6 5.Qxg6+ Bg7 6.Rh8+! Kxh8 7.Qh7#. In this line Black can refuse the first rook but after 4...Kf8 5.Rxf6 Ke7 6.Qxf7+ Kd8 7.Rh7 he must give up one of his own rooks to avoid mate. Simple, beautiful and incisive!
As Emanuel Lasker correctly advised, when you have found a good move, wait – there may be a better one!