Before the action of the play begins, what have Betty Parris and her friends been doing?

On the night before the play begins, Betty Parris and her cousin, Abigail Williams, as well as some other local girls, went dancing in the forest with Reverend Parris's Barbadian slave, Tituba.  Apparently, Mrs. Putnam sent her daughter, Ruth, to Tituba to ask the slave to conjure the spirits of her dead babies in order to figure out who might have been responsible for their deaths.  Mrs. Putnam's terrible luck -- seven out of eight of her children died shortly after birth -- has led her to believe that one or more of her midwives must be a witch, and she is desperate to learn of some reason for her children's deaths.  In addition, Abigail also drank a charm to kill Elizabeth Proctor, the wife of Abigail's former lover, and one of the girls danced naked.