15. Ne2, b4;
(Not 15...a4?; 16. Nad4)
16. f4, Ba6; 17. Rf3?
(Extricating himself from the pin by 17. Rf2, Be2; 18. Rd2, a5 is better, although Black maintains the initiative.)
17...Be2; 18. Qe2, a4; 19. Nd2, Nd4; 20. Qd3, Qc2!?
(Black heads into a winning endgame, eschewing the stronger win of the exchange by 20...Nf3! because after 21. Nf3, he didn't realize the strength of 21...d5!)
21. Qc2, Nc2; 22. Nc4, d5!
(With White's active knight gone, his disorganized pieces can't stop Black's advance.)
23. Ne5
(If 23. ed5, Bd4+ with a big advantage.)
23...Be5; 24. fe5, d4!
This passed pawn, the knight on c2, the advanced queenside pawns, and Black's material advantage give him a strong attack.
25. Bg5?
(This attempt at counterplay fails, but 25. Bh6, Rfd8 just drives the rook behind the passed pawn, but 25. b3, ab3; 26. Rb3, Nc6; 27. Bf4, Rcf8; 28. Rd2, Ne3; 29. Be3, de3; 30. Re3, Ne5; 31. Rb3 allows white to hang on with a disadvantage.)
25...Nc6; 26. Rc1, b3; 27. ab3, ab3; 28. Bf6, Rfc8; 29. h4?!
(29. Bf1 is better.)
29... Ne3; 30. h5
(White is lost.)
31... Nb4; 31. Rb1, gh5; 32. Bf1, h6!?
(This keeps the bishop off the c1-h6 diagonal, although 32... Rc2 is just as good.)
33. Kf2?! Rc2; 34. Ke1? R8c8; 35. Be7, Rc1! 36. Rc1, Rc1; 37. Ke2, Nf1; 38. Rf1?
38. Bb4 loses more slowly.
38... d3!
(This finishes things quickly.)
39. Kf2, d2; 40. Bb4, Rf1; 41. Kf1, d1(Q); White resigns.