"I wish Uncle Dock hadn't seen us there to-day. It'll make it awkward now if we ever go back. He has told us to stay away, and now he'll be suspicious if he ever sees us around there again." "We might tell dad what we know about the place." But Frank vetoed this suggestion. "I'd rather work along our own lines until we get something more definite," he said. "If we get some real evidence we can tell dad about it. So far we have nothing to go on but our own suspicions." All the way back to Bayport, the Hardy boys discussed the various aspects of the case, and although they agreed that the mysterious activities of the three men at the old mill tended to indicate almost anything but scientific endeavors, they realized that if they investigated too thoroughly they might get into serious trouble. "We'll just wait a while and keep our ears open," Frank decided. "If those fellows are in the counterfeiting game they'll do something to give themselves away. And then we'll be right on the job." When the boys arrived home they amused themselves in the gymnasium in the barn for some time, had an impromptu boxing match and finally, after a shower bath, went down the street. It was a sleepy Saturday afternoon and the city was very quiet. "Nothing much doing around here," remarked Frank. "We should have stayed out in the country." "We could go out in the motorboat for a while." "Fine. Let's go." But at that moment they heard the whistle of the afternoon express. Like most boys, they had a weakness for trains. There was a fascination about the great locomotives that held them spellbound and they liked nothing better than to watch the trains that passed through Bayport and to speculate on the towns and cities they had come from or were bound for. At times when school became exceptionally distasteful they had often gone down to the railway station and wished they could board the first train that came by, to travel on to strange countries. Somehow, they had never been so daring as to do this, common sense invariably coming to the rescue, but the lure of locomotives and shining rails still held them in its grasp. They moved down the street toward the station and came out on the platform just as the express was pulling in. Idly, they watched the few passengers who emerged from the coaches, envied the engineer who was lolling majestically in the cab, watched the conductor in his smart uniform, and looked at the people who were boarding the train. Suddenly Frank nudged his brother. "Isn't that Markel?" he asked. Joe followed his glance. Near the steps of one of the Pullman coaches was a familiar figure, with cap pulled down over his eyes. There was no mistaking the fellow; he was indeed Markel, one of the associates of Uncle Dock at the old mill. What particularly attracted the boys' attention, however, was the fact that Markel carried a bulky paper package under his arm.