“Everybody always knows something," said Adam, "even if it's something they don't know they know.”

“Never tell all you know—not even to the person you know best.”

“I don't know. I don't know at all. And that's what's frightening the life out of me. To have no idea....”

“Evil is not something superhuman, it's something less than human.”

“You do think you know about everything," said her husband. I do," said Tuppence.”

“Conversations are always dangerous, if you have something to hide.”

“Don't you know, you idiot, that that is what every fool of a woman says about her child?Miss Bulstrode's thoughts.”