Mary started to scream, and then the curtains parted further and a hand appeared, holding a butcher's knife. It was the knife that, a moment later, c… - Robert Bloch

It was the knife that, a moment later, cut off her scream.

Evil exists everywhere. Sometimes I think our limited senses are designed to protect us from awareness of its presence. We trust them to provide us with knowledge but it may be that they block out realization of horrors we cannot bear.

Norman Bates heard the noise and a shock went through him. It sounded as though somebody was tapping on the windowpane. He looked up, hastily, half prepared to rise, and the book slid from his hands to his ample lap. Then he realized that the sound was merely rain. Late afternoon rain, striking the parlor window.

You didn't really forget. It's just that you don't want anyone to come, you hope they don't come.