In this episode of Harper's Island, the following happens. When reading from Wakefield's prison journal we learn that he and Abby's mother had a child. And so everyone no presumes that Abby is that child. Everyone works together when another member of the party goes missing. It's during this search that Abby finds Madison. She is alive and appears to be unharmed.
When they get back to the hotel, Madison asks Abby if she enjoyed the game as the man who took her said she would. When asked what man she says you know your father, the Sheriff. Why would he take Abby and why was Henry covered in all that blood at the end of the last episode? We still don't have an answer.