Had the man turned around as he made his way toward a dark and forbidding house on Thirteenth Street, not far from Fourth Avenue, he might have caught sight of two shadows skulking along not fifty feet behind him. But, at that, he would have to have been pretty quick--for Maxwell was taking no chances on losing his prey and he had cautioned the policeman not to make a sound. When their quarry ascended the steps of No. 247 Riley started to move after him, but the Department of Justice operative halted him. "There's no hurry," stated Maxwell. "He doesn't suspect we're here, and, besides, it doesn't make any difference if he does lock the door--I've got a skeleton key handy that's guaranteed to open anything." Riley grunted, but stayed where he was until Maxwell gave the signal to advance. Once inside the door, which responded to a single turn to the key, the policeman and the government agent halted in the pitch-black darkness and listened. Then from an upper floor came the sound for which Maxwell had been waiting--the first golden notes of a violin played by a master hand. The distance and the closed doorway which intervened killed all the harsh mechanical tone of the phonograph and only the wonderful melody of "Drigo's Serenade" came down to them. On tiptoe, though they knew their movements would be masked by the sounds of the music, Riley and Maxwell crept up to the third floor and halted outside the door from which the sounds came. "Wait until the record is over," directed Maxwell, "and then break down that door. Have your gun handy and don't hesitate to shoot anyone who tries to injure Buch. I'm certain he's held prisoner here and it may be that the men who are guarding him have instructions not to let him escape at any cost. Ready? Let's go!" The final note of the Kreisler record had not died away before Riley's shoulder hit the flimsy door and the two detectives were in the room. Maxwell barely had time to catch a glimpse of a pale, wan figure on the bed and to sense the fact that there were two other men in the room, when there was a shout from Riley and a spurt of flame from his revolver. With a cry, the man nearest the bed dropped his arm and a pistol clattered to the floor--the barrel still singing from the impact of the policeman's bullet. The second man, realizing that time was precious, leaped straight toward Maxwell, his fingers reaching for the agent's throat. With a half laugh Mort clubbed his automatic and brought the butt down with sickening force on his assailant's head. Then he swung around and covered the man whom Riley had disarmed. "Don't worry about him, sir," said the policeman. "His arm'll be numb half an hour from now. What do you want to do with th' lad in th' bed?" "Get him out of here as quickly as we can. We won't bother with these swine. They have the law on their side, anyway, because we broke in here without a warrant. I only want Buch."