In The Scarlet Letter, Hawthorne uses the scaffold scenes to separate the story into three parts. Something different happens on the scaffold in each instance, and these differing events succeed in helping the reader understand the evolution of the plot and the characters.
The first mention of the scaffold comes early in chapter 2, as the public gathers before it to see Hester Prynne forced to put herself on display in front of the townspeople as part of the penalty for her crime of adultery. Hester is supposed to be humiliated and at first attempts to hide the scarlet “A” on her bosom, but then changes her mind and asserts herself, as she will throughout the rest of the story:
"She took the baby on her arm, and with a burning blush, and yet a haughty smile, and a glance that would not be abashed, looked around at her townspeople and neighbors."
Hester’s actions upon the scaffold show that she will not allow her sin to define her for the rest of her life, no matter how the other townspeople may feel about her.
The second scaffold scene occurs about halfway through the story, in chapter 12. The Reverend Dimmesdale is overcome with guilt at his part in Hester’s adultery. His presence on the scaffold symbolically links him to the sin for which only Hester has suffered publicly. However, as Hawthorne shows in this passage it is possible to suffer privately, as Dimmesdale has done, to an even greater degree.
"And thus, while standing on the scaffold, in this vain show of expiation, Mr. Dimmesdale was overcome with a great horror of mind, as if the universe were gazing at a scarlet token on his naked breast, right over his heart."
The third and final scaffold scene occurs at the end of the story, in chapter 23. Its purpose is to provide the story with something of a “happy” ending by showing Dimmesdale’s realization of God’s purpose. Dimmesdale has just delivered a sermon that could be regarded as the best of his career. He knows that events are coming to an end, and he also now knows that Roger Chillingworth is aware that he is the unnamed father of Hester’s child and has been secretly torturing him for years. Moments before his death on the scaffold, he explains to Hester how all of his sufferings have served to bring him closer to God:
"God knows; and he is merciful! He hath proved his mercy, most of all, in my afflictions. By giving me this burning torture to bear upon my breast! By sending yonder dark and terrible old man to keep the torture always at red-heat! By bringing me hither, to die this death of triumphant ignominy before the people! Had either of these agonies been wanting, I had been lost forever! Praised be his name!"
In each case, Hawthorne has used the scaffold to advance his story, as well as mark its beginning, middle, and end. This serves to unify the story, since the scaffold is a symbol of punishment, as well as provide a final irony as Dimmesdale realizes that his punishment is also his salvation.