Read the excerpt from "The Adventure of the Mysterious Picture." All this was half muttered to myself, as I hastily slipped on my clothes; which having done, I groped my way out of the room, and down-stairs to the drawing-room. Here, after tumbling over two or three pieces of furniture, I made out to reach a sofa, and stretching myself upon it determined to bivouac there for the night. What technique does Irving use to build suspense in the excerpt?