He rode down Pennsylvania Avenue as far as Fourteenth Street, where he alighted and walked the remaining distance to the Treasury Building, entering one of the side doors with an air and display of interest often observed in the crowds of tourists to be seen in this vast building at that hour of the day. No observer would have supposed him other than a sight-seeing stranger, viewing Uncle Sam’s great money box and financial institution for the first time in his life. Something like five minutes later, nevertheless, he entered one of the numerous offices without the ceremony of knocking, and blandly addressed a clerk who turned from his desk to see who had entered. “I suppose Chief Welden is inside?” he said inquiringly. “Yes, sir,” bowed the clerk. “I will take in your card, or name, if----” “Don’t trouble,” interrupted the old gentleman, smiling. “I am his uncle. He is expecting me. I will go right in.” He did not wait for an objection, had any been forthcoming, but opened a near door and walked into an adjoining private office. It was quite large and elaborately furnished. But the only occupant was an attractive, clean-cut man seated at a large, roll-top desk. “Don’t rise, Welden,” said the old gentleman, after closing the door. “Have a look at my card. It will supply the needed link. Even you are not likely to recognize me.” Chief Welden, then the head of the United States secret service, glanced at the card the speaker displayed for a moment and then coolly returned to his own pocket. It bore the name of the celebrated New York detective--Nick Carter. Chief Welden laughed. “Gracious!” said he, pointing to a chair with one hand and extending the other. “No, indeed; I would not recognize you. You’re the limit, Nick, when it comes to giving one a surprise. Why did you come in this rig?” “A summons direct from the nation’s chief executive, Welden, must be occasioned by something of vast importance,” Nick replied, drawing up a chair and cordially shaking hands with the treasury official. “It imposes corresponding circumspection upon one of my vocation. I decided to drop in here under cover and learn what is wanted of me.” “I knew that the president had communicated with you and I was expecting you to show up during the day,” said Chief Welden, more gravely. “I got the special-delivery letter this morning.” “When did you arrive?” “Half an hour ago.” “Alone?” “As you see,” said Nick evasively. Chief Welden swung round in his swivel chair, so as to directly face the noted detective. There had been other times when the keen and clever men under his direction had been baffled by perplexing problems, resulting in an appeal to the famous New York detective; but judging from Welden’s expression at that moment, none could have been more important than that which had occasioned this summons of Nick Carter to Washington, an appeal direct from the president himself.