In Act III, scene i of The Crucible, Abigail accuses Mary of lying in her testimony because she wants to keep her own ruse going. She still hopes that somehow, these false accusations of witchcraft will help her to win John Proctor in the end. She also likes the sense of power she gets from the attention she is receiving in court - the judges hang on her every word, and the other girls follow her lead.
Mary, prior to testifying in court, had been one of those girls following Abigail's lead, but once away from that "mob mentality" and confronted by John Proctor, she comes to court to admit she has been pretending - that she has really not seen any spirits; it's all been an act. She hopes to clear Goody Proctor's name with this testimony, but Abigail has other ideas.
When Abigail returns to court, Judge Danforth confronts her, saying:
"Your friend Mary Warren has given us a deposition. In which she swears that she never saw familiar spirits, apparitions, nor any manifest of the Devil. She claims as well, that none of you have seen these things either.... Abigail Williams, rise. Is there any truth in this?"
Abigail vehemently denies the charge and goes on to also accuse Mary of lying about the poppet (which Mary had explained to the judge was her own and that Abigail had seen her sewing it in court). Abigail, still trying to make the court believe the injury she suffered in her side was due to the "voodoo technique" used by Goody Proctor, claims that when she worked for the Proctors, "Goody Proctor always kept poppets."
Soon, Judge Hathorne brings the attention back to Mary, saying:
"You say you never saw no spirits, Mary, were never threatened or afflicted by any manifest of the Devil or the Devil’s agents? ... And yet, when people accused of witchery confronted you in court, you would faint, saying their spirits came out of their bodies and choked you."
When Mary admits, "That were pretense, sir," Hathorne asks her to "pretend to faint now" to prove what she is saying. However, Mary cannot faint at their request, and explains:
"I used to faint because… I… I thought I saw spirits.... But I did not, your Honor.… I heard the other girls screaming, and you, your Honor, you seemed to believe them and I… It were only sport in the beginning, sir, but then the whole world cried spirits, spirits, and I… I promise you, Mister Danforth, I only thought I saw them but I did not."
At this, Danforth calls upon Abigail Williams again to "search (her)heart" to see if it is possible that "the spirits (she has) seen are illusion only." Abigail angrily retorts to the judge:
"I have been hurt, Mister Danforth; I have seen my blood runnin’ out! I have been near to murdered every day because I done my duty pointing out the Devil’s people—and this is my reward? To be mistrusted, denied, questioned like a… Let you beware, Mister Danforth—think you to be so mighty that the power of Hell may not turn your wits?!—beware of it!"
After this, she begins her insidious act, shivering and looking at Mary, saying that "a wind, a cold wind has come," and accusing Mary of "send(ing) this shadow on (her)."
This act is only brought to an end by Proctor's accusation that Abigail is "a whore," and the focus after this shifts to the alleged illicit relationship the two have shared.