The Effects of Sin in The Scarlet Letter Sin is the main theme in the Scarlet Letter. All of the characters in the book were somehow affected by the main sin, which was adultery. The three main characters were the most widely affected, and their whole lives were molded by the way they dealt with the sin. The sin surrounds, encloses, and strangles them. There was no escaping from its harsh consequences. Hester Prynne's sin was as an adulteress, and the result of this was that she had to wear the scarlet letter "A." She feels that her sin has taken away everything she had, and given her one thing in return;