Hi Graciey,
Have you made it through to Part Three already? Have you tried going back to an earlier save game at the beginning of Part Three and replaying exactly by the walkthrough, so that nothing is missed? It's difficult to say what you might have overlooked that's stopping you from progressing, since there are so many people to speak to and items to examine.
Alternatively there are some saved games
HERE that you could use to get you past your stuck point.