In Act Three, Danforth questions Mary Warren and Abigail Williams in court about Abigail's testimony against Elizabeth Proctor as well as Mary's new accusations that Abigail and the other girls are not being truthful.  He says to Abigail, 

A poppet were discovered in Mr. Proctor's house, stabbed by a needle.  Mary Warren claims that you sat beside her in the court when she made it, and that you saw her make it and witnessed how she herself stuck her needle into it for safe-keeping.  What say you to that?

This is, of course, the story that Mary herself told in Act Two, when Ezekiel Cheever came to the Proctors' home to arrest Elizabeth, without knowing that Abigail had accused Elizabeth of sending out her specter to stab Abigail with the needle.  Abigail asserts that Mary's story is a lie.  Further, she tells the court that "Goody Proctor always kept poppets," a statement which we know to be untrue from the conversations that occurred in Act Two.  Elizabeth Proctor has not owned a doll for many, many years, until Mary gave her this one that she made as a gift.  Likewise, as John tells the court, "Mary Warren swears she never saw no poppets in [his] house [...]."  This is really all Abigail has a chance to say in court about the subject at this time because, shortly after, John brings up the girls' dancing in the forest and the topic of testimony shifts.

In Act Two, Herrick (the Marshall) and Cheever (clerk of the court) come to the Proctor's house to search for a poppet (doll). They find the poppet that Mary Warren had given to Elizabeth. Abby put Mary up to this. They planted the poppet there to be used as evidence against Elizabeth. Cheever and Herrick find the poppet and discover that there is a needle in it. Cheever is astounded. But John and Hale ask him what this needle or the poppet could possibly signify.

Cheever relates a story about how Abigail fell to the floor in Parris's house, claiming she had been stabbed by Elizabeth, even though Elizabeth was not there. Abigail is trying to show how Elizabeth used some form of Voodoo or witchcraft to stab her by stabbing the poppet. Whatever harm she (Elizabeth) does to the poppet, Abby will feel; this is Abby's claim. This is another way Abby tries to accuse Elizabeth of being a witch. Cheever relates the story: 

The girl, the Williams girl, Abigail Williams, sir. She sat to dinner in Reverend Parris’s house tonight, and without word nor warnin’ she falls to the floor. Like a struck beast, he says, and screamed a scream that a bull would weep to hear. And he goes to save her, and, stuck two inches in the flesh of her belly, he draw a needle out. And demandin’ of her how she come to be so stabbed, she - to Proctor now - testify it -were your wife’s familiar spirit pushed it in. 

In Act Three, in the courthouse, Mary Warren affirms that she made the poppet and put the needle in herself. Abby denies this, insisting that the poppet is Elizabeth's and thereby, accusing her of stabbing the poppet and stabbing her (Abby) in the process.