14. ... Qe6
This move is an attempt to free the f6 knight and the f8 bishop. Black is desperate to get some activity for his pieces, which have been trapped nearly the entire game.
While White may appear to be down a rook, the fact that Black's kingside rook and bishop haven't entered the game effectively means that White is playing with more material than Black, not less.
15. Bxd7+
A clearly winning move for White, as Black's defense crumbles.
15. ... Nxd7
This move leads to our next diagram, and a stunning conclusion to the game. First, though, we should look at what happens after Black's other try.
If Black plays Qxd7, he avoids getting mated, but will find himself in a completely lost position. White's best line is 16. Qb8+ Ke7 17. Qxe5+ Kd8 18. Bxf6+ gxf6 19. Qxf6+ Ke8 20. Qe5+ Kd8 21. Qxh8 Qxd1+ 22. Kxd1, with a simple win. It's a long line, but one worth playing out on a board if you cannot follow it in your head. Notice how Black's moves are all nearly forced; if Black isn't careful, he can easily be mated.
