who is the only person who notices a change in the minister? what does this person think has happened to the minister?

Mistress Hibbins overhears him complain that he is haunted and tempted. She stops and asks Dimmesdale when he will be returning to the forest—so that she may join him. He tells her he is never going back, to which she replies that at midnight they will soon be together in the forest. She then departs, leaving Dimmesdale terrified of what he has done with Hester.