In Act 4 of "The Crucible," what does Parris think Abigail has done?
In addition to robbing him of his life's savings -- thirty one pounds -- after breaking into his strongbox, Reverend Parris believes that his niece, Abigail Williams, has boarded a ship with her best friend, Mercy Lewis. Abigail told him that she would be spending the night at Mercy's house, and Mercy had told a similar lie to her parents: that she was sleeping at Parris's house. Parris tells Danforth that his daughter, Betty, had heard Abigail and Mercy talking about ships the week before, and so this is what has led to his conclusion that the two girls have stolen all his money in order to leave Salem permanently, by the speediest method possible. He thinks that, since Abigail would have been aware of the rebellion against the witch trials in Andover, a nearby town, she would probably have developed a fear of a similar rebellion in Salem, as a rebellion could have gone badly for her as the lead accuser.
In Act IV of The Crucible Reverend Parris has discovered that Abigail has broken into his safe, stolen money, and fled town. Parris understands that this reveals her true character, and that she is only thinking of her own survival. Abigail's actions reveal that Parris and the others assisting in the investigation should be weary of Abigail's many accusations. This move begins to reveal that the entire investigation is merely a dangerous house of cards built on the villagers hysteria.
In Act IV of "The Crucible", Parris believes Abigail stole all his money and left town for good. This seems to confirm that Abigail cannot be trusted and that her charges of witchcraft against so many people should be viewed with suspicion. Parris also confirms that he is very concerned with money, but it is Abigail who seems to have escaped the consequences of her actions.