What clues has Hawthorne offered his reader in order to prepare him or her for the revelation of the scarlet letter on his chest?

Just as Hester is about to toss her scarlet letter away, she feels a burning in her chest. The narrator asks, who in the world could have imagined that a scarlet letter has marked them both,

"Just as Hester is about to toss her scarlet letter away, she feels a burning in her chest. The narrator asks, who in the world could have imagined that the scarlet letter marked them both, the woman near the pillory and the saintly minister?"