Nice, Bg5!! Great move, didn't see that earlier. fxg5 is off the cards because Rxf7 forces mate.
exf5 gives Bxf6+, And of course Qg8 also fails to Bxf6+, Rg7, and Rg5 is curtains for black.
Yes, Bg5 is the move. Here is the whole game:
http://www.chessgames.com/perl/chessgame?gid=1022130
Congratulations to Mad Mac MacMad for being the first to find the solution and also for one of the most impressive growth spurts I've seen in some time! User 70949
Well done Mr Lasker - just when I was beginning to think that just about any move wins for White, you managed to find one which loses. The simple exf5 refutes Rg3, e.g.
1. Rg3 exf5
2. Qxf7 Nxf7
3. Bg7+ Kf8
4. Nxf6+ Qxf6
5. Bxf6 Kf8
and Black is just a piece up.