The Nh5 still hangs, whilst there is now a threat of 21.d6. White has a healthy extra pawn, and went on to win.

Losing the Bd8, which is X-rayed down the d-file by the white rook, would obviously be catastrophic for Black, because he would be unable to get out his queenside pieces. The only question is where the white knight should go, and the answer is easy to find:

On 25.b4, there would follow 25...b6, and there is nothing decisive.
Also not very effective is 25.Kf4 Re8 26.Nxe4 b6 – the black bishop comes out to d7, and Black can defend.

White is trying to weaken the dark squares in the opponent’s camp, so as to organise an attack on the king. But, the weakening of his own construction is something he has not noticed, and Black begins to land counterblows on the light squares:

After 18.Nc3, White has to lose precious time to regain the central pawn: 18...fxe5! 19.Rd1 Be8! (the right square to keep the d5-pawn under attack) 20.Ne4 Rc8 21.Qxe5 Rf5!, and ...Rf5xd5.

This move is not so easy to spot from a distance, when playing 17.e5.

White resigned.

The white Nd4 is clearly loose. It is not hard to see that it covers the f3-square. Thus, Black found the idea...

The most tenacious.
If the sacrifice is accepted, then after 21.gxh3 Rad8 22.f4 Rxd4 23.fxe5 Qxe5 24.Re2 Re6, followed by ...Rg6+ and ...Ne6, all Black’s pieces are attacking, and this attack assumes a decisive character.

As a result of the tactical operation, Black has won a pawn without any compensation. In addition, the white king is weak.