Martha Corey was tried as a witch after a group of girls accused her of witchcraft in Salem, Massachussetts in 1692. This was a time of great disorder for the little Puritan town because in the beginning of the year Abigail Williams and Betty Parris, two girls living with the town's minister were said to have begun displaying bizarre behaviors. They spent time with Tituba, their Carribean slave who had confessed to spending time with the Devil.
The girls continued to make accusations. Martha Corey, an upstanding member of the congregation was early on their list of the accused. The girls pretended to be afflicted by her and mocked her every move.
Today, many believe this was indeed pretend. Several of the girls involved with Abigail and Betty came forth with confessions of false accusations years later.
Hope that helps a little bit!