“It had all begun on the elevated. There was a particular little sea of roots he had grown into the habit of glancing at just as the packed car carrying him homeward lurched around a turn. A dingy, melancholy little world of tar paper, tarred gravel, and smoky brick. Rusty tin chimneys with odd conical hats suggested abandoned listening posts. There was a washed-out advertisement of some ancient patent medicine on the nearest wall. Superficially it was like ten thousand other drab city roofs. But he always saw it around dusk, either in the normal, smoky half-light, or tinged with red by the flat rays of a dirty sunset, or covered by ghostly windblown white sheets of rain-splash, or patched with blackish snow; and it seemed unusually bleak and suggestive, almost beautifully ugly, though in no sense picturesque; dreary but meaningful. Unconsciously it came to symbolize for Catesby Wran certain disagreeable aspects of the frustrated, frightened century in which he lived, the jangled century of hate and heavy industry and Fascist wars. The quick, daily glance into the half darkness became an integral part of his life. Oddly, he never saw it in the morning, for it was then his habit to sit on the other side of the car, his head buried in the paper.One evening toward winter he noticed what seemed to be a shapeless black sack lying on the third roof from the tracks. He did not think about it. It merely registered as an addition to the well-known scene and his memory stored away the impression for further reference. Next evening, however, he decided he had been mistaken in one detail. The object was a roof nearer than he had thought. Its color and texture, and the grimy stains around it, suggested that it was filled with coal dust, which was hardly reasonable. Then, too, the following evening it seemed to have been blown against a rusty ventilator by the wind, which could hardly have happened if it were at all heavy. ("Smoke Ghost")”