Abigail Williams is a primary character in The Crucible by Arthur Miller, and she is the driving force behind the Salem Witch trials in this play. She and some of the other girls in town were in the forest last night, which would have been a serious and punishable offense in this time and place. In fact, they would be whipped if they were caught, which is why Betty is faking an illness this morning. Abigail admits:
Uncle, we did dance; let you tell them I confessed it - and I’ll be whipped if I must be. But they’re speakin’ of witch-craft. Betty’s not witched.
As the play continues, new information is revealed, however, and we learn a little more about last night's activities. Some of the girls were dancing, and at least one of them was running around naked. We know this because the Reverend Parris was also in the forest last night and saw them.
Parris, Abigail's uncle, gets quite stern with her and says this:
Now tell me true, Abigail. And I pray you feel the weight of truth upon you, for now my ministry’s at stake, my ministry and perhaps your cousin’s life. Whatever abomination you have done, give me all of it now....
Abigail lies and says there is absolutely nothing more; however, when the girls are alone, Betty tells the truth about what Abigail was doing in the forest.
You drank blood, Abby! You didn’t tell him that!
You did, you did! You drank a charm to kill John Proctor’s wife! You drank a charm to kill Goody Proctor!
This information would certainly get Abigail a much harsher punishment than a whipping. Witchcraft is a hanging offense, as evidenced by the punishments which will be meted out during the upcoming trials.
Abigail wants to conceal last night's activities in the forest because while all the girls would be punished, Abigail would likely be hung as a witch. That is a pretty powerful motivation to want to keep this information a secret, but it is an act which is going to cost more than twenty innocent people their lives.