In act 1 of The Crucible, Abigail drinks blood as a charm to bring about Elizabeth Proctor's death because she is envious of Elizabeth and desires John Proctor.
When Reverend Parris demands to know what the girls have done the previous night, Abigail does not tell him everything. However, after Betty awakens, she reminds Abigail about what she has done.
BETTY: You drank blood, Abby! You didn’t tell him that!
ABIGAIL: Betty, you never say that again!
BETTY: You did, you did! You drank a charm to kill John Proctor’s wife! You drank a charm to kill Goody Proctor!
ABIGAIL, (She smashes Betty across the face) Shut it! Now shut!
Soon after this exchange, Mr. Putnam and his wife arrive and ask Reverend Parris questions about what has occurred to cause their Ruth to be "struck dumb." Abruptly, Putnam says to Parris, "You have discovered witchcraft." The Reverend Parris asks him not "leap to witchcraft." He also asks Putnam to leave so that he can pray before Mr. Hale comes to consult with him. Soon after the departure of Goody Putnam and her husband, Reverend Parris asks Abigail what occurred the night before. He also inquires if spirits were called upon during the night. Abigail denies any witchcraft but she accuses the servant Tituba and Ruth Putnam of such actions.
Later, Abigail talks with the other girls, informing them that Reverend Parris knows that Mercy was naked and that Tituba was waving her arms over a fire and uttering strange words. She also tells them that Goody Putnam has informed Parris about Tituba's conjuration of Ruth's sisters. Abigail then orders the girls to only admit that they danced and that Tituba conjured Ruth Putnam's sisters. They must not reveal anything else, or she will "come to [them] in the black of some terrible night" and make them wish they "had never seen the sun go down." Abigail threatens the girls because she realizes that if they are accused of witchcraft they could be severely punished. Additionally, her uncle, Reverend Parris, would be ruined.