After 1. d4 d5 2. Nc3 Nf6 3. Bg5 Nbd7 4. Qd3 h6
White isn't supposed to play 5. Bxf6 because of the line 5. ...Nxf6 6. e4 dxe4 7. Nxe4 Nxe4 8. Qxe4 c6!
Black threatens ...Qa5+ followed by ...Bf5, equalizing (at least). If 9. O-O-O then ...Qd5 =.
9. Bd3 has been tried, but ...Be6 is supposed to equalize. I was wondering if white could try 9. Bd3 Be6 10. c4!? Qa5+ 11. Kd1
Here black has a few reasonable options.
11. ...Qa4+ 12. b3 Qa3 13. Kc2 (or 12. ...Qb4 13. Kc2)
11. ...g6 12. g4 h5 13. Nf3!? hxg4 14. Ne5 looks interesting
11. ...O-O-O will probably transpose, as black is probably going to play both ...g6 and ...Qa4+ at some point.
It seems to me that white might maintain an edge here.