Well, in Act II we learn that Rebecca has been accused of witchcraft, specifically the supernatural deaths of Goody Putnam's children. We learn that she has been arrested and is being taken to jail along with Martha Corey and now Elizabeth Proctor to await trial.
In Act III Rebecca's husband, Fancis, attempts to convince the court that Rebecca and the others are innocent and that Danforth is being deceived by the girls. By the time he returns to the court with documentation to support his claim, Rebecca and Martha have already been tried and found guilty of witchcraft.
Proctor brings a long list of 91 character witnesses who support Rebecca and Martha and petition the court for their release. This tremendous show of support proves again how much Rebecca and Martha are respected in the community.
Francis is upset when all 91 character witnesses are called in for questioning by the court since he personally promised them that no harm would come from their signing his petition.
You can find an excellent summary of The Crucible at the link below: