At the same time he put out one hand, and it fell upon a dusty shelf on one side of the room. “Turn your back a moment, boy,” he commanded. Billy did so, and while he looked away he was certain that the stranger did something. When again he looked around the man was standing at his ease and his face was as calm as ever. “Look yonder,” suddenly cried the boy, pointing at the window. “There it is again.” The stranger turned in an instant, and then looked at the street Arab. “I see nothing at the window,” he said. “It’s gone now. That’s the second time I saw it there.” “A face, was it, boy?” “Yes; the face of the man who killed Mother Flintstone!” “Then it’s not far off.” With this the stranger ran out of the place, and Billy heard him in the narrow court beyond. “In the name of Satan, who is he?” ejaculated the boy, while he waited for the man’s return. His question was followed by a sharp report, and in a second the boy was outside. He smelled powder the moment he opened the door, and then a human figure fell at his feet. Billy sprang back with a cry and heard a half-suppressed oath and flying footsteps. “Say, boy,” said a voice, as the little fellow stooped over a prostrate man on the bricks. “Did you see him?” “Only a glimpse.” “Well, he’s got me--just as I expected. But he didn’t get the documents.” “What documents?” “Mother Flintstone’s. They’re here.” The wounded speaker laid one hand on his left breast. He tried to rise, but sank again to the stones, and Billy could only look on, white-faced and breathless. “You want a doctor and the perlice,” he said at last. “Neither one,” growled the man through set teeth. “I don’t want them, I say. I’m not dead yet, though they gave me a close call to-night. Help me up. There, you see I can stand all right. I feel better already. I’m worth ten dead men, and in an hour I’ll be worth fifty. Come, let us get out of this.” Billy was not loath to go, and they glided from the scene and struck the street in a few seconds. “Great Cæsar!” cried the boy, falling back from the man the moment he got a glimpse of him in the lamplight. “Be you the devil or Tom Walker----” The man stopped the boy by throwing his hand to his face. The black beard was gone and the skin was smooth, and this was what had called forth the street urchin’s exclamation. CHAPTER XVIII. THE FATE OF A SPY. Under the ground at last Mother Flintstone passed from the minds of many. The hovel she had occupied in Hell’s Kitchen got other tenants and the crime was forgotten. Not by everybody, however, for in the mind of more than one person the old woman whose life no one seemed to know beyond a few years was of some importance.