What was that sound? It can be hard to tell if it was even something human. Prone to happen at night, or otherwise in the dark, especially in the Haunted House, the Abandoned Area and the like, all places where wandering off is probably foolish. Has a magnetic attraction for characters, even ones who are not the Fearless Fool. An opening not so innocuous as Follow the White Rabbit. Repetition, especially if no one ever figures out what it was, can turn it into Hell Is That Noise.