John Proctor has forbidden Mary to go to the court in Salem, where witch trials are taking place, but she goes anyway. John is angry when she returns and threatens to whip her if she does this again. Mary says,

I am sick, I am sick, Mr. Proctor. Pray, pray hurt me not. My insides are all shuddery; I am in the proceedings all day, sir.

When John asks her more questions, it comes out that what is going on in Salem is worse than he had thought. Thirty-nine people are accused of witchcraft, not fourteen; at least one has been sentenced to hang; and Mary, easily impressionable, is sure that an old, poor widow, Sarah Good, who is accused of witchcraft, used a spell to try to choke her in court.

Mary also brings out a rag doll she said she made for Elizabeth in court and mentions that she protected her mistress from a witchcraft allegation.

Mary's declaration about being "sick" works on a several levels. Most obviously, she is using feeling sick to keep John from hurting her. But on a deeper level, the sense of sickness and shuddering inside she feels is a physical manifestation of the psychological unease she is experiencing at what she is participating in. Mary is a weak character who, on one hand, knows what is going on is a lie but lacks the strength of character not to be swept up in the hysteria. She is torn between loyalty to the Proctors and not wanting to go against Abigail. Her sense of sickness foreshadows her role in the sick proceedings that will destroy lives.

The above quotation is spoken by Mary Warren in act 2 of The Crucible. Mary has just returned to the Proctor residence after spending all day in Salem, where she is an official of the court.

As a member of Abigail's little gang, Mary has been called to give testimony in front of the judges presiding over the witch trials. What was previously a weak, timorous young girl has suddenly become the center of attention, one of the key sources of information about the alleged plague of witchcraft sweeping the town.

When Mary comes back from court, John Proctor is absolutely furious with her. He grabs her and threatens to give her a good whipping. He's hit the roof because Mary, by spending all day in court, has shirked her responsibilities as his servant.

The essential weakness of Mary's character comes out in her desperate plea to John not to hurt her. She tells him that she's sick; in fact, she tells him this twice. What this appears to indicate is the enormous psychological stress that the witch trials are having on Mary. One shouldn't forget that, intellectually and emotionally, she's still a child and so is understandably finding it increasingly difficult to handle such a stressful situation.

Of course, Mary's not the only one suffering psychological damage from the witch trials. Those innocent people that she and Abby have falsely accused are also doubtless sick from their terrible ordeals. But that Mary is herself a kind of victim of the witch craze sweeping Salem is an indication of how this collective insanity has taken on a momentum all of its own, to the extent that it's now starting to have a negative impact on one of the witch hunt's major figures.