In the last act of the play, Rev. Hale is not effective in accomplishing what he has returned to do in terms of saving the innocent lives of the condemned, but his reappearance in the play's conclusion is extremely effective in developing Miller's themes and in emphasizing the tragic elements of the drama. Also, Hale as he is presented in Act IV provides a stark contrast to the deeply flawed characters of Parris and Danforth.
When Hale returns to Salem in Act IV, he is a far different man from the confident minister who first arrived in the community, as well as from the disillusioned one who quit the court in anger and frustration. When he comes to the jail to counsel with the accused, he is broken in body and spirit and filled with despair. His guilt is enormous, for he accepts the role he played in destroying others. The fact that he had acted in good faith at the time does not comfort him. He seeks redemption by returning to Salem to save lives by begging the accused to confess, even though lying is a grave sin.
Through Hale's character in the final act, Miller emphasizes the terrible, senseless human tragedy that has played out in Salem. Hale's final scene with Abigail Proctor is filled with raw pain, both his and hers, as he struggles desperately to convince her to save John's life by securing his false confession. So deep is his anguish that it matches her own as her husband is about to die.
Hale also stands as another character who affirms the idea that a person of conscience must stand against forces of injustice. Proctor, among others, stands against the court; Hale stands against both the court and his church. His rebellion is powerful indeed, for he chooses to risk his very soul rather than remain silent in the face of great injustice. His example of moral courage reinforces the play's theme, and surely calls to mind those during the McCarthy era who would not stand up for justice.
In his personal despair and unselfishness, Hale also provides a stark contrast to and condemnation of Parris and Danforth. These characters have destroyed lives and, for whatever personal reasons, have continued to do so, refusing to see the truth of their actions.
Hale's presence in Salem at the play's conclusion very effectively pulls together the various threads of the drama and serves to bring the play to its heartbreaking conclusion.