Why is Mary Warren embarrassed and fearful when John Proctor enters the room in Act 1?
There are several reasons why Mary Warren fears Proctor in Act 1. First of all, he had forbid her to leave the house. (He is her boss, he has the right to do that.) Secondly, he seems a rather fearsome character. While Mary Warren tries to defend herself by pointing out she had just come to see a great wonder in the world, he threatens her right then and there by saying:
I'll show you a great doing on your arse one of these days. Now get you home; my wife is waitin' with your work.
I think this proves that Mary Warren was there against the Proctors' will. She knows that this means trouble for her. Like a child who has done something wrong, Mary is at such a loss for dignity that she quickly departs.
The way that Abigail treated her prior to Proctor's entrance might also suggest that Mary had a weak character to begin with, it is as if she rarely stood up for herself. This is important to know and understand as the play proceeds.
In Act One, John Proctor visits Reverend Parris's home to see Betty and inquire about the rumors of witchcraft. When John Proctor enters Betty's room, Mary Warren is startled and leaps out of fear once she sees Proctor. Arthur Miller writes that Mary can barely speak because she is both embarrassed and afraid. Mary Warren is John Proctor's servant, and he instructed her earlier to stay at his home and not travel into town. Proctor immediately questions Mary and asks why he is even paying her if she is not at home working. Proctor is a rather intimidating man, and Mary Warren is depicted as a sensitive, timid girl. Mary feels embarrassed and afraid of John because she knows that she is disobeying him and has been caught. When Mary Warren tells John that she has only traveled to Salem to see "the great doings in the world," John threatens to beat her and demands that she head home immediately. Mary Warren instantly obeys John and leaves Reverend Parris's home.