In one of my works in progress, a teenage girl has a loving father who adores her in return, and she refuses point-blank to believe any of the really horrible accusations that are being made against him. When she finds his private journal and discovers the terrible truth that yes, he really is what people are claiming he is, it shatters her world forever.

I got the idea from the BTK Killer, who when not torturing and killing his victims was a loving husband and father whose own daughter never suspected a thing.