Black to move! How should black proceed?
Unless something is wrong with the diagram, what does ...h5 do? To me the correct move is ...c5 threatening the knight on b4.
The problem with 1......c5 is that it allows white to get the queen back to a1 to break black's attack. You have to note that black is down a piece in the starting position, so winning the knight won't necessarily win the game, and I am not even convinced that black can win the knight either. For example:
1... c5 2.Qa1 cb4?? 3.Re1+- the queen is pinned to the rook at e8.
If black tries to move the rook first, then you likely get...
1... c5 2.Qa1 Rc8 3.Re1 Qd2 4.Qd1 Qd1 5.Rd1 cb4 6.Nb4 Bg4 7.h3 Bh3 8.Bf3 with approximate equality, but only white plays for the win given black's two weak isolated pawns on the queenside.
I didn't fully flush it out that night because it was just before my bedtime, and I made a complete mess of it anyway, but here is what 1.....h5 does:
The threat was 2.....Qf2+ 3.Kf2 Re2+ 4.Kf3 Bg4+ 5.Kf4 Bh6# . Continuing from 2.Bg2 above:
2.....fg2! 3.Qa1 Rf8 4.f4 Qf1+ 5.Rf1 gf1(Q)+ 6.Qf1 Bf1 7.Kf1 g5 should win for black, though there might be better moves than 4.....Qf1+, just what I would play over the board if I didn't want to do a deep calculation.
To clean it up a bit:
1.......h5 threatens 2......Qxf2.
Threatens 2.Qxf2 since then 2....Kf2 3.Re2+ Kxf3 is met by 4.Bg4+ followed by 5.Bh6#.
I think black can avoid the mate with with 1.....Bg2 giving up the piece, but it might still be a mate in there somewhere, but I'm not seeing immediately.
- ... Qxf2+ 2. Kxf2 Re2+ 3. Kg1 f2#