For a three-act plot analysis, put on your screenwriter’s hat. Moviemakers know the formula well: at the end of Act One, the main character is drawn in completely to a conflict. During Act Two, she is farthest away from her goals. At the end of Act Three, the story is resolved.
Act I
When the book opens, Lily Owens is struggling with an angry daddy and only shadowy memories of her mother (whom she, um, accidentally killed). Plus, it's her birthday, and nobody seems to care. To break up the tedium/sadness of her life, she decides to accompany Rosaleen, the woman who looks after her, into town. Rosaleen, who is African American, is making the trek to register to vote for the first time.
Unfortunately, Rosaleen and Lily get into a tussle with some white men immediately upon arriving in Sylvan and end up in jail. Lily is allowed to leave when her dad comes to get her, but she soon realizes that she is in her own kind of prison living with him. Also, more importantly, she realizes Rosaleen is in terrible danger in the jail. So, she runs away and breaks Rosaleen out. They then head to Tiburon, South Carolina, where Lily tracks down some women who knew her mother, the Boatwright sisters, and finagles a way to stay with them. However, she doesn't reveal her true identity (or the fact that Rosaleen is a fugitive from the law) just yet . . .
Act II
Lily and Rosaleen enjoy life with the Boatwrights, although they are aware that things can't go on like that forever. Lily knows she's eventually going to have to talk to August, the eldest Boatwright sister (and family matriarch), about her mother—you know, since that was her whole purpose in tracking the Boatwrights down—but she avoids having that talk for a good chunk of the novel.
Then, things kind of start blowing up. Zach, Lily's close friend and one of August's assistants, gets arrested for a crime he didn't commit, which prompts August's sister, May, to commit suicide. Lily finally decides the time has come to give August her complete backstory and ask about her mother. Lily is devastated to learn that her mother had left Lily behind when she left Lily's father.
Act III
Lily eventually gets over her feelings of hurt and abandonment and things get better. There is a little mini-crisis right before the end of the novel when her father finally comes looking for her and threatens to drag her home. However, she and August manage to convince him to let her stay on there. And don't worry—things worked out for Rosaleen, too; when the book ends, a local lawyer (and friend of the Boatwrights) is helping fix her legal problems back in Sylvan.