What important event might have happened prior to the beginning of The Face on the Milk Carton?
Janie Johnson sees an advertisement on a milk carton one day. She is confused because the ad says that Jennie Springer is missing, but it is a picture of a younger version of herself.
She asks her parents what it could mean. They tell her that they have a daughter, Hannah, who joined a cult and gave birth to a daughter after being mated to another cult member. She is that daughter. She is really their granddaughter. They took custody of her to prevent the cult from finding her after Hannah returned to the cult.
That still leaves the mystery of Jennie Springer. Janie hunts down the Springer family and is struck by the family resemblance. It is obvious that they are her blood family.