A singular cry welled from the millionaire’s throat, the revolver slipped to the floor and he sank back in the chair in a dead faint. The stranger leaned forward and opened the drawer, and seeing something there he transferred it to an inner pocket. CHAPTER XVII. BACK TO THE RED SPOT. When Carter and Mulberry Billy reached the street at the foot of Carter’s stairs the boy pointed toward a cab just driving away. “He must be in that,” said Billy. “I saw him talking to a man from the cab window just now----” “The man whose face you saw at the window of Mother Flintstone’s den, Billy?” “The same bloke.” The detective looked after the cab as it rounded a corner and then turned again to the boy. “But the man who was spoken to from the cab?” queried the detective. “He’s gone, too.” In another instant there stepped from a doorway a few steps distant a man at whom the boy pointed excitedly. “That’s him, Mr. Carter!” he exclaimed, as the man thus singled out coolly lit a cigar. Carter eyed him for a moment and then looked away. The fellow walked off and the boy of the street watched him with much curiosity. “Could you keep him in sight for me, Billy?” asked the detective. “Just as if I’d lose him on purpose!” Billy hurried away and watched the smoker with all the keenness he could bring to bear upon the matter. For some time the boy was led a merry chase, for the man at first seemed to suspect that he was watched, but at last he appeared to think that he had baffled the young shadower, for he became bold and sauntered along at his ease. Billy saw him walk up the steps of a noted clubhouse, and then stepped back to wait for his reappearance. For this purpose the boy stationed himself in a doorway near at hand. An hour passed, and while many came out of the club this particular one did not, and the street Arab grew a little impatient. “Seems to me he’s going ter roost there,” said Billy to himself. “I’m booked for this doorway all night if he does, for I intend to keep my agreement with Mr. Carter--to watch that man till doomsday.” All at once there sounded above the boy footsteps on the stairs, and as he looked around he was pounced upon eaglelike by a hand that seemed to sink into his bones. “Ouch!” cried the boy, as he drew back. “Not a chirp, you young imp,” hissed a voice, as he was pulled up over the steps. Billy, of Mulberry Street, was dragged up the stairs and down a long corridor, after which he was pulled into a room by his tormentor. He heard the door locked behind him, and then the gas was quickly turned on. Then he was jammed roughly into a chair, after which he got a look at the man who had caught him. It was not the man he had watched, but quite another person, and Billy wondered why he had caught him. “Spying, weren’t you?” said the man coolly. “Who are you?” demanded Billy. “And don’t you know you’ve no right to treat me this way?”