How is the Preger family important to the plot in the novel, God’s Radar?

Among the members of the Stafford Hill church, Roxie's neighbors, the Pregers, are the most important to the story, because they introduce her parents into the church. Bess, their daughter, befriends Roxie, trying her best to convert her. They seem to be the ideal Christian family, although Roxie discovers that not all is well behind the cheerful family facade.