In chapter 17 Hester is determined to disclose to Dimmesdale that the man whom he has come to know as his physician, Roger Chillingworth, is actually Hester's husband Roger Prynne.
Revealing this information entails many things. First, that Hester lied to Dimmesdale, after all, even though she did this because she had promised Chillingworth secrecy. The second thing it entails is that Chillingworth no doubt has ulterior motives that are bad for Dimmesdale, hence, Dimmesdale is completely trapped. The last thing it entails is that life for Dimmesdale may change forever, as he is directly dependent upon Chillingworth not telling his secret.
Hester felt quite guilty about what she did. She asked Dimmesdale for forgiveness over and over. However, it is in Dimmesdale's reaction that we find that there is a wide gap that separates him from Hester; this gap consists on the way in which they individually perceive their connection.
I freely forgive you now. May God forgive us both. We are not, Hester, the worst sinners in the world. There is a sinner even greater than this sinful priest!
Dimmesdale responds that he does forgive Hester. He admits that he had wronged her too, after all. Yet, he compares the wrong that they have done together to the wrong that Chillingworth is committing against him. This concerns Hester, who is adamant in that what she and Dimmesdale had was not a bad thing.
Never, never!” she whispered. “What we did had a holiness of its own. We felt that! We told each other so. Have you forgotten that?
After Dimmesdale responds that he has not forgotten, a sudden charm comes upon Hester and Dimmesdale which really does not amount to much. However, they are now both guarded from what evils Chillingworth will bring to them.