In stories, when someone behaves uncharacteristically, we take it as a meaningful, even pivotal moment. If we are surprised again and again, we have to keep changing our minds, or give up and disbelieve the writer. In real life, if people think they know you well enough not only to say, 'It's Tuesday, Amy must be helping out at the library today,' but well enough to say to the librarian, after you've left the building, 'You know, Amy just loves reading to the four-year-olds, I think it's been such a comfort for her since her little boy died'—if they know you like that, you can do almost anything where they can't see you, and when they hear about it, they will, as we do, simply disbelieve the narrator.