The opening scene...

Yeah right, but I'll say this, it was the scariest part of the movie. The opening really creeped me out. What was it's relationship to the rest of the movie? Who knows, maybe just that evil was near. I read William Peter Blatty's The Exorcist awhile ago and it had a series of "vignettes" prior to the actual story that were representations on how evil manifests itself. Maybe the opening was the same thing?

They were most likely friends of Nell's father who took her in after following the massacre at the farm. The purpose of the opening was to serve as a bridge connecting the two films.

The 'bridge' idea makes sense. But honestly...it was pretty unnecessary. And explained nothing.
Plus, like the poster above said..it may have been the best part of the movie.
Which is not good.

It was obvious to me that Nell had wandered into their house and crawled into bed with the husband. That gnarly looking thing on the counter was Nell. She was in shock and delusional from the ordeal in the woods. The couple called the cops/authorities/whatever and that's how she ended up in the girl's home.

But, yes, it was the best part of the whole movie. Which is sad.