Read the excerpt from "The Adventure of the Mysterious Picture." The expression was that of agony—the agony of intense bodily pain; but a menace scowled upon the brow, and a few sprinklings of blood added to its ghastliness. Yet it was not all these characteristics—it was some horror of the mind, some inscrutable antipathy awakened by this picture, which harrowed up my feelings. What technique does Irving use to build suspense in the excerpt?