I understand that the town folk is basically a cult, that Sarah and Eric were born on the same day Ana Harris died, and that Ana Harris is the small red head girl depicted throughout the film. What I am confused about is how all of this pieces together and forms a plot?
Judging from online descriptions, this movie seems to be rather incoherent.
I've found this blog post which tries to speculate about how it all ties together:
Here’s where the story starts to wither and we are shown some haphazard scenes wherein the brother-in-law gets stabbed by his girlfriend, only to stop bleeding miraculously and inter-cut with will this is a scene where the pregnant woman gets into a car accident.
Somewhere along the lines, it is revealed that both brother and sister (who are actually twins), can see ghosts and were protected by ghosts in their childhood. There are also butterflies involved somehow which I suppose is supposed to be a symbol of some sort.
Needless to day, people start to die one by one, the pregnant woman is hunted by the law officers because of her birthmark and there are some cheap CGI effects thrown in that take away the tense mood of the movie.
Eventually everyone dies and the story behind the birthmark is never actually reasonably explained. In the climax, the woman goes into labor, gives birth to a stillborn and her acting midwife convinces the mother to kill herself to save the baby.
So she bleeds and the baby comes to life.
I had to actually pause and be with my thoughts after the movie was over and decided that the woman was a reincarnation of the girl who had been killed and buried. Or perhaps people with the mark are somehow connected?
Another blog post lists numerous unexplained parts of the movie:
Ok, so much for the STUFF YOU CAN UNDERSTAND. Do you want to foray down the path of the PLOT? It's so scary it will make you horny.
There’s a backwoods cult. They have a thing for women with moon-shaped birthmarks. No one knows why.
The wife has a moon-shaped birthmark. Apparently they want her and her baby. No one knows why.
But there’s also the ghost of a girl from 1979 who had the same birthmark. She’s got a red fro thing going on. Apparently the cult captured her, but then the main baddie, a guy they call the preacher, let her go. The preacher ends up in jail and is burned to death. He’s also some kind of DNA experiment. Now HE’S a ghost as well. And he’s sort of a good ghost in that he’s trying to protect the moon-shaped birthmark woman. Except that he’s also sort of a bad ghost in that he’s killing all of her friends.
But it isn’t clear that red fro is a good ghost either, since she caused the pregnant protagonist to drive off the road. Really, the ghosts in this movie are frustratingly inconsistent.
And so the cult is out after the moon-shaped birthmark woman, and someone, either the cult or one of the bipolar ghosts, is dismembering her friends and mounting them in rooms around the burned out prison.