“Well, supposing you went into a shop, say, and you knew the proprietress had a son who was the spivvy young juvenile delinquent type. He was there listening while you told his mother about some money you had in the house, or some silver or a piece of jewellery. It was something you were excited and pleased about and you wanted to talk about it. And you also perhaps mention an evening that you were going out. You even say you never lock the house. You're interested in what you're saying, what you're telling her, because it's so very much in your mind. And then, say, on that particular evening you come home because you've forgotten something and there's this bad lot of a boy in the house, caught in the act, and he turns round and coshes you.” […] “[M]ost people have a sense of protection. They realize when it's unwise to say or do something because of the person or persons who are taking in what you say, and because of the kind of character that those people have. But as I say, Alison Wilde never thought of anybody else but herself— She was the sort of person who tells you what they've done and what they'ye seen and what they've felt and what they've heard, They never mention what any other people said or did. Life is a kind of one-way track—just their own progress through it. Other people seem to them just like—like wallpaper in a room." She paused and then said, "I think Heather Badcock was that kind of person.”

— The Mirror Crack'd from Side to Side by Agatha Christie