This proved to be the case. When the boys reached the police station they found Chief Collig and Detective Smuff in the midst of a game of pinochle and averse to being disturbed. When they inquired if there had been any further information regarding the rug merchant, Chief Collig shook his head. "We're following up some clues," he said gravely; "but there hasn't been any more trace of him." "Not a trace," corroborated Detective Smuff, with a portentous frown. "Do you think he'll be arrested?" asked Frank. Chief Collig looked up. "Of course he'll be arrested," he declared. "Didn't I say we're followin' up clues? We'll have the fellow behind the bars all right." "I'm workin' on the case myself," said Detective Smuff, examining his cards wearily. "Rely on us," advised the chief. "Your play, Smuff." The boys retired. Somehow, they got the impression that the Bayport police department was not exerting a great deal of effort to try to capture the fraudulent rug buyer. CHAPTER XX A NOTE OF WARNING Three days later, Fenton Hardy, who had been away from home on business, received a note. No one saw the man who left it at the door. The Hardy boys were at school and Mrs. Hardy was busy in the kitchen. She heard the front doorbell ring and went to answer it. But when she opened the door there was no one in sight. She looked out and saw a man walking briskly down the opposite side of the street. A woman with a baby-carriage was strolling past the house, and farther down the street two men were standing talking on the corner. Somewhat surprised, and imagining that her ears must have deceived her, she was about to close the door when she became aware of a white object that had fluttered to her feet. It was a cheap envelope, sealed, and with the name of Fenton Hardy written on it in pencil. Mrs. Hardy picked it up, examined it curiously, then brought it into the house and placed it on the table in her husband's study. It was not an unusual occurrence to have letters left at the door in this manner, as occasionally anonymous letters were left for the detective, giving him hints or advice concerning cases on which he was engaged. To most of these he paid no attention, although sometimes valuable information was brought to his notice in this manner. This, Mrs. Hardy judged, was another such communication, which was why the person who delivered it had been careful to hurry away after ringing the bell. Mr. Hardy did not return home until late that afternoon. He had been over to Barmet village where the Federal authorities were closely watching two men thought to be in league with the counterfeiters. Mr. Hardy had followed one man to a near-by city and seen the fellow pass a small package to a woman in black, who had quickly disappeared in a crowd. But the noted detective knew the woman and knew where she could be located when wanted.