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
Shame, Shame, Shame
Hester is publicly shamed for her sin but refuses to name her partner-in-crime. Her long-lost husband returns, discovers her adultery, and, not content with having his wife shunned and ostracized for the rest of her life, starts plotting his revenge.
Act II
Run, Run, Run
Roger Chillingworth is possessed by his need for vengeance, and Reverend Dimmesdale grows steadily weaker as a result of his guilt. You know, kind of like Chillingworth is a guilt-vampire and Dimmesdale is his victim. Hester, meanwhile, manages to raise her child, support herself, and stay charitable while all the mean girls in town are gossiping about her behind her back.
Eventually the stress gets to be too much, and Hester decides to mix things up by revealing the truth to Dimmesdale and basically asking him to run away with her. You go, girl!
Act III
Die, Die, Die
Dimmesdale finally confesses (publicly, natch), collapses, and dies. Roger Chillingworth dies soon after, since guilt-vampires die without guilt to feed on.
Hester and Pearl escape Puritan life thanks to Chillingworth's fortune, which he leaves to Pearl, and go to the Old World, i.e., Europe. But eventually, Hester returns to the scene of her crime—er, passion and triumph: the Massachusetts Bay Colony.