From Protector of the Grey House:
“Think of this carefully: is this really something you would have done on any other occasion? Has there been an occasion where you wondered if there was a hidden room?”
“Joseph, I don’t know. It’s never come up.”
“Why hasn’t it?”
She paused. “What?”
“In all the years you’ve lived in this house, why have you never wondered about a hidden room? You’ve seen that hallway thousands of times. Why did you never, until this instance, feel the need to question its lack of doors?”
Natalia turned and went to the bed. She sat down in silence for a moment. The moment grew longer, and Joseph’s voice came through.