What motivated Abigail and Mercy to run away?

Abigail of course knows her relationship with Proctor is long dead. The main reason is that she fears the town's retribution. Too many innocent people have died at the hands of the court and her wretched lies. In the nearby town of Andover, the witch court was run out of town. She knows that people will be after her. Abigail convinces Mercy things are just as bad for her.