The Heroine Falls under the Shadow of a Dark Power
The heroine is Bone and the "dark power" is Glen. Easy, right? But it isn't immediately clear that Glen is a "dark power" until he molests her; in fact, Anney seems to think that Glen will help them all become a big happy family.
Things Seem to Go Reasonably Well
In this case, the threat of Glen never really goes away. After Bone ends up in the hospital and Anney leaves Glen for the first time, it seems like maybe things will change, but we find out pretty quickly that they don't. Bone finds other ways of dealing with the abuse, mostly by staying away from home, going to her aunts' places, and hanging out with Shannon Pearl—but the danger posed by Glen is always looming in the background.
Eventually it Approaches Again in Full Force until the Heroine is Seen Imprisoned in a State of Living Death
Glen's temper seems to get worse and worse. Anney at first seems to stand her ground and protect Bone when Glen hurts her, but then as time goes on, it seems like she is more interested in protecting Glen than Bone. Glen also seems to get more savage with Bone, as he learns that Anney will tolerate it and that Bone won't tell Anney.
When it Seems that the Dark Power Has Completely Triumphed…
The real moment when it seems like Glen has triumphed is when he rapes Bone, because even her family's knowledge of the abuse doesn't seem to be able to save her from Glen.
But Finally Comes the Miraculous Redemption
Well, redemption is one way of describing it. It's miraculous in the sense that Anney is finally made to confront what she has avoided confronting. Bone also does get away from Glen for good, so she is at least released from the dark power. Of course, in doing so, she also loses Anney, which is heartbreaking, but Bone handles the loss of Anney with a saint-like degree of understanding.