The Devil in the White City pg. 102

Here was one of the creepiest passages I have read so far:

One night during this period Holmes asked Ned a favor. He led him to the big vault and stepped inside, then told Ned to close the door and listen for the sound of his shouting. "I shut the door and put my ear to the crack," Ned recalled, "but could hear only a faint sound." Ned opened the door, and Holmes stepped out. Now Holmes asked Ned if he would go inside and try shouting, so that Holmes could hear for himself how little sound escaped. Ned did so but got back out the instant Holmes reopened the door. "I didn't like that kind of business," he said.

Why anyone would even want a soundproof vault was a question that apparently did not occur to him.