What purpose does the framing of narratives serve?

“The Custom-House” is a stand-alone section or frame narrative of the novel. It resembles more a tract or a personal essay than an introduction to a piece of fiction, but it offers plenty of insights that will support the rest of The Scarlet Letter. For one thing, we gain a sense of why the narrator feels the need to tell the story. As a man of youth and vigor, he feels somewhat at odds with the Puritan nature of his society. He himself seems to feel a deep resentment for the strict fidelity to rules and values that would deem his whole personality, and his ambition to write, as frivolous or even sinful. The discovery of the Scarlet Letter sets the flashback into motion. This device has been used commonly in literature—that is, when someone discovers an ancient artifact, it retains some of its power, and the finder has the responsibility to put it to rest. In this case the narrator, despite his torpid slumber of insipid duty to job and country, has been awakened to his mission, and he accepts it, revealing to us the mystery of the letter, no matter the consequences for him and his community.