Reverend Hale comes to the jail to try to save John Proctor from going to the gallows. He hopes to either convince Proctor to confess and save himself or convince Elizabeth to persuade Proctor to confess. He also makes an attempt to sway the judges to change their minds about Proctor's sentence.
Hale has changed his mind about the accusations of witchcraft in Salem, realizing that Abigail Williams and the other girls have been lying and their claims are a fraud. He once believed, fully, in the truth of those claims, but when he arrives at the jail he has been convinced otherwise. To his credit, he is willing to see that he was wrong.
[Hale] is a man of integrity who, although at times misguided and overzealous, is willing to change his mind when confronted with the truth.
However, Hale's earlier zeal and belief in the accusations of witchcraft lead to John Proctor's death sentence. For this reason, he returns to Salem and attempts to save Proctor.
Hale feels that it will be his fault if Proctor dies.