Black could have forced the draw with the surprise sacrifice 28...Nd3!, but misses this opportunity and allows White to grab the advantage with the pawn sacrifice 30. b4! White may well have had a winning advantage after 31. bxc5, and initiates a clearly decisive pinning combination with 35. Rxg4!

My analysis with Fritz 8 follows:

28...Raf8?!

[28...Nd3! 29.Qxd3 a) 29.Rxd3?? Qxf2+–+; b) 29.Bxd3 Qxf2+ 30.Kh1 Qh4+ 31.Kg1 (31.Rh3 Qxe1+–+) 31...Qf2+ 32.Kh1 Qh4+ 33.Kg1 Qf2 is a draw by threefold repetition; c) 29.R1e2 Nxf2 30.Qc3 Qxc3 31.Rxc3 Raf8 32.a5 h5 33.g3 Kg6 34.Rce3 Nd1 35.Re7 Bf5 36.Bg2 Nc3 37.R2e3 Rxe7 38.Rxe7 Rf7 39.Re3 Na2=; 29...Qxf2+ 30.Kh1 Qh4+ 31.Kg1 (31.Rh3?? Qxe1–+) 31...Qf2+ 32.Kh1 Qh4+ 33.Kg1 Qf2 with a draw by threefold repetition]

29.Ne4 Qg6 30.b4! Bf5

[30...cxb4? 31.Qb2+ Kg8 32.Qxb4 ; 30...b6!? 31.bxc5 (31.Qb2+?! Kg8 32.bxc5 bxc5 33.Qb6 Bf5 34.Ng3 Bc2 35.Qxa6 (35.a5?! h5 36.Nh1 h4 37.Qxa6 Qf6 38.Rc1 Bg6 39.Rce1 g3–+) 35...h5 36.Qc6 h4 37.Nh1 Nh3+ 38.gxh3 gxh3+ 39.Ng3 h2+ 40.Kxh2 Rxf2+ 41.Kg1 hxg3 42.Bh3 Kh8 43.Re8 Be4–+) 31...bxc5!? 32.a5 Bf5 33.Qb2+ Kg8 34.Ng3 h5 35.Nxf5 Qxf5 36.g3 Nh3+ 37.Bxh3 gxh3 38.Kh2 h4 39.Qd2 Qg6 40.f4 Rg7 41.Qf2 Kh7 42.Rg1 Qg4 43.Qc2+ Kh8 44.Qd3 Kg8 45.Qf1 Rb8 46.Qf2 Rb4 47.gxh4 Qxg1+ 48.Qxg1 Rxg1 49.Kxg1 Rxc4 50.Re6 ]

31.bxc5! and White is winning 31...Bxe4 32.Qxe4 dxc5 33.g3! Qxe4

[33...Nh5!? 34.Qxg6+ Kxg6 35.Bd3+ Kg7 36.Re6 Nf6 37.Rb6 h5 38.a5 Rd8 39.Re5 ]

34.Rxe4 Ng6

[34...Nh3+!? 35.Bxh3 gxh3 36.f4 b5 37.axb5 axb5 38.cxb5 Rb8 39.Rb1 Rfb7 40.Kh2 Rxb5 41.Rxb5 Rxb5 42.Kxh3 Rb7 43.Rc4 Rc7 44.d6 Rd7 45.Rxc5 Rxd6 46.g4 Rd1 47.Kg3 Rd3+ 48.Kh4 Rf3 49.Rc7+ Kf6 50.Rc6+ Kg7 51.Rc4 Rf1 52.Rc7+ Kf6 53.Rc6+ Kf7 54.Kg3 Rh1 55.Rc5 Kg6 56.Kg2 Rh4 57.Rc6+ Kg7 58.Kf3 Kf7 59.Rc1 h5 60.g5 ]