The cab turned into the narrow cobbled streets of Chinatown, past the dark windows, Chinese stores and restaurants, a region that, deserted now, appeared in the early morning quiet ominous rather than peaceful. Dark alleys opened out frequently--alleys which coiled like snakes past cellar entrances, noisome rears of tottering tenements, to grease-fingered doors as impassive as the stolid faces of guards who drowsed behind them asleep to all save those who knew the deadly pass-word. Paradoxical doors which shut in, instead of out, danger! But Saul knew them and they knew Saul. He knew further the haunts of beginners, where opium is high and the surroundings are fairly clean, he knew the haunts of the confirmed, where opium is cheaper and where surroundings do not matter at all. Also he knew Wun Chung, who does not smoke, but who, being rich, controls the trade and so keeps in touch with all who buy. On the way to Chung's Saul made one stop. With Donaldson at his heels, he darted down a side street, pushed open, without knocking, a dingy door, went up a flight of stairs, along a dark hallway and down another flight, where he was stopped by a shadow. The big man spoke his name, and the shadow turned instantly from a guard to an obsequious servant. He opened the door and Saul strode across a narrow yard, stooping to brush beneath the stout clothes-line hung with blankets, an innocent appearing wash, which however served as an effective barrier to any one who might approach at a run. They entered the rear of a second tenement which faced a parallel street, but which, oddly enough, had no entrance to its rear rooms from the front. Another shadow rose before them only to vanish as the round red face of Saul appeared. He pushed on into a long, low-ceilinged room lined with bunks, the air heavy with the acrid dead smoke of opium. "Light," demanded Saul. The sleepy proprietor brought a kerosene lamp, the chimney befouled with soot and grease. It was an old trick. These fellows protect their customers and through a sooted chimney the feeble light makes scarcely more than shadows in which it is very difficult to identify a man. Seizing the slant-eyed ghoul by the arm Saul held the lamp within an inch of the yellow face, so close that it burned. "Don't try such fool things on me, Tong," he warned. "Bring me a light."