When Dimmesdale meets Pearl, he realizes that she is his daughter and the sin he must keep hidden. He is the minister of the town and he committed adultery with Hester. Although the two love each other, he knows that it has to be kept hidden. He goes on to say that Pearl plays two dual roles in both of their lives.
"This child of its father's guilt and its mother's shame hath come forth from the hand of God, to work in ways upon her heart, who pleads so earnestly, and with such bitterness of spirits, the right to keep her. It was meant, doubtless, as the mother herself hath told us, for a retribution too; a torture, to be felt at many an unthought of moment; a pang, a sting, and ever recurring agony, in the midst of a troubled joy! Hath she not expressed this thought in the garb of the poor child, so forcibly reminding us of that red symbol which sears her bosom?"
Dimmesdale is telling us that both he and Hester, harbor guilt and shame over their child, but they also have deep love and affection for her. He thinks that Pearl was sent by God to show the love between the two of them, and yet in a way, Pearl herself, will always be the real scarlet letter. Every time they look at her, they are thrown back into their guilt over what happened. We do see, however, at the end, that the three of them find love for each other, and that is a beautiful thing.