Don't fall for this trap

Heheh, played a game today where my opponent likes to play a lot of trappy moves. Fell for an early trap but hung on until move 38 where I had an opportunity to equalize. The correct defense to the trap was 4 Nxd4. Then after exd White can castle K-side.

[Event "ICC 30 30"]
[Site "Internet Chess Club"]
[Date "2006.04.25"]
[Result "0-1"]
[ECO "C50"]
[WhiteElo "1374"]
[BlackElo "1384"]
[PlyCount "84"]
[TimeControl "1800+30"]

1. e4 e5
2. Nf3 Nc6
3. Bc4 Nd4
4. Nxe5 Qg5
5. Ng4 d5
6. Be2 Bxg4
7. Bxg4 Nxc2+
8. Qxc2 Qxg4
9. O-O O-O-O
10. f3 Qg6
11. d3 dxe4
12. dxe4 Bd6
13. g3 h5
14. Nc3 Ne7
15. Nb5 h4
16. Nxd6+ Qxd6
17. Bf4 Qb6+
18. Kg2 Ng6
19. Bg5 f6
20. Bxh4 Nxh4+
21. gxh4 Rxh4
22. Rad1 Rdh8
23. Rh1 g5
24. h3 Qe6
25. Rc1 c6
26. Kf2 Rxh3
27. Rxh3 Qxh3
28. Ke3 g4
29. Qe2 Qh6+
30. f4 Qh3+
31. Kd2 g3
32. Rg1 Rg8
33. Qg2 Qd7+
34. Ke3 Qe6
35. b3 f5
36. e5 Qg6
37. Qh3 g2
38. Rxg2 Qxg2
39. Qxf5+ Kc7
40. Qf7+ Kb6
41. e6 Rg3+
42. Kd4 Qd5# {White checkmated} 0-1