What is Cheever’s mission during the events of act 2 in The Crucible?

Ezekiel Cheever and Herrick, the town marshal, arrive with a warrant for Elizabeth’s arrest. Hale is surprised because, last he heard, Elizabeth was not charged with anything. Cheever asks if Elizabeth owns any dolls, and Elizabeth replies that she has not owned dolls since she was a girl. Cheever spies the doll Mary Warren gave her. He finds a needle inside it. Cheever relates that Abigail had a fit at dinner in Parris’s house that evening. Parris found a needle in her abdomen, and Abigail accused Elizabeth of witchcraft. Elizabeth brings Mary downstairs. Mary informs the inquisitors that she made the doll while in court and stuck the needle in it herself.