John Proctor has ordered Mary Warren, his family's hired help, to stay at the house today and not go onto Salem Village. She, however, has disobeyed him, telling Elizabeth Proctor that she is "an official of the court now," implying that she has an obligation to be there. Mary knows that those who are accused of witchcraft are always convicted, and those who are convicted of witchcraft are always put to death unless they confess. Proctor becomes angry at Mary for refusing to obey him, and he threatens her with whipping. In order to escape his wrath, Mary tells them that Elizabeth's name was "Somewhat mentioned" in the court, and she takes the credit for "sav[ing] her life." When asked about Elizabeth, Mary testified that she has "never see[n] [a] sign [Elizabeth] ever sent [her] spirit out to hurt" anyone. Since Mary lives with the Proctors and spends so much time with them, her testimony was believed and the subject of Elizabeth Proctor was dropped.

In act two, Mary Warren arrives back at John Proctor's home after spending the day acting as a court official in Salem. Mary Warren is John Proctor's maid, and she neglects her duties in order to be an official during the witch trials. She is typically a timid girl but has a newfound air of confidence after being selected to such a prestigious position in the court. John Proctor is upset that Mary Warren neglected her duties and disobeyed him by traveling into Salem. When he threatens to whip Mary, she stops him by saying, "I saved her life today!" (Miller, 63). Earlier that day, Abigail Williams had mentioned Elizabeth in conjunction with witchcraft in front of the court. However, Mary Warren testified that she never witnessed Elizabeth Proctor engage in witchcraft or harm anyone before. Given the fact that Mary Warren spends the majority of her time in Elizabeth's household, Deputy Governor Danforth and Judge Hathorne believe her testimony and dismiss Abigail's accusations. Therefore, Mary Warren's testimony saves Elizabeth from being arrested for witchcraft. Later in act two, Abigail Williams accuses Elizabeth Proctor of sending her spirit after her, and deputies of the court arrest her.

When Mary returns to the Proctor home after her day in the Salem court, John angrily threatens to whip her. He is angry because she has defied his order to stay away from Salem. Moreover, he is shocked and irate that his teenage servant is involved in the deadly accusations that have already condemned 39 villagers. 

John becomes enraged when Mary tells him "the Devil's loose in Salem," and he raises the whip, announcing "I'll whip the Devil out of you!" Mary stops him with five words: "I saved her life today!"

Elizabeth is stunned to hear that her name has come up in court, but Mary assures them both:

"But I said I never see no sign you ever sent your spirit out to hurt no one, and seeing I do live so closely with you, they dismissed it."

Unfortunately, Mary overestimates her authority with the court and underestimates the deviousness of Abigail Williams. Though Mary will not divulge the information that it is Abigail who made the accusation, the Proctors understand who is behind the accusation.

Mary acts as a character witness before the court. She tells them she has not seen the witchcraft Elizabeth has been accused of. Her words literally did save her life, for a time.

Mary informs Elizabeth and John that she told the council "...I said I never see no sign you ever sent your spirit out to hurt no one, and seeing I do live so closely with you, they dismissed it."