He also loses after 21...Qd8 22.Bxc4 (or 22.Bf8 Kxf8 23.Qh6+ Kg8 24.Ngf6+ exf6 25.exf6+–) 22...bxc4 23.exd6 Qxd6 24.Ndf6+ Kh8 25.Bg7++–.

The white queen hopes to protect the king by covering the h3-square. But Black interfered with this defence:

White’s hopes are bound up with perpetual check on the c8- and f5-squares. Consequently, Black needs to find a way to drive the white queen off this diagonal. In the game, Black missed a chance to end the game beautifully:

Having seen the winning idea, it is easy to find the right way of executing it: first, the white king is driven to a square where the black pawn will queen with check.

Winning.

If we look at the opposition of queens on the e-file from a more imaginative standpoint than the usual one, and note that even though the bishop on e5 is pinned, it can move anywhere, we soon find a nice finish:

And the game ends.

Any means by which White can get his queen to h4 or h5 are good. He finds a way:

27...Qxb8 28.Qxh4 and soon mate.