The sensation of being followed is at first annoying; then a pleasant zest creeps into it, and in Armitage’s case the reaction was immediate.  He was even amused to reflect that the shadow had chosen for his exploit what is probably the most conspicuous and the best-guarded spot in America.  It was not yet ten o’clock, but the streets were comparatively free of people.  He slackened his pace gradually, and threw open his overcoat, for the night was warm, to give an impression of ease, and when he had reached the somber facade of the Treasury Building he paused and studied it in the glare of the electric lights, as though he were a chance traveler taking a preliminary view of the sights of the capital.  A man still lingered behind him, drawing nearer now, at a moment when they had the sidewalk comparatively free to themselves.  The fellow was short, but of soldierly erectness, and even in his loitering pace lifted his feet with the quick precision of the drilled man.  Armitage walked to the corner of Pennsylvania Avenue and Fifteenth Street, then turned and retraced his steps slowly past the Treasury Building.  The man who had been following faced about and walked slowly in the opposite direction, and Armitage, quickening his own pace, amused himself by dogging the fellow’s steps closely for twenty yards, then passed him.

When he had gained the advantage of a few feet, Armitage stopped suddenly and spoke to the man in the casual tone he might have used in addressing a passing acquaintance.

“My friend,” he said, “there are two policemen across the street; if you continue to follow me I shall call their attention to you.”

“Pardon me—­”

“You are watching me; and the thing won’t do.”

“Yes, I’m watching you; but—­”

“But the thing won’t do!  If you are hired—­”

“Nein!  Nein! You do me a wrong, sir.”

“Then if you are not hired you are your own master, and you serve yourself ill when you take the trouble to follow me.  Now I’m going to finish my walk, and I beg you to keep out of my way.  This is not a place where liberties may be infringed with impunity.  Good evening, sir.”

Armitage wheeled about sharply, and as his face came into the full light of the street lamps the stranger stared at him intently.

Armitage was fumbling in his pocket for a coin, but this impertinence caused him to change his mind.  Two policemen were walking slowly toward them, and Armitage, annoyed by the whole incident, walked quickly away.

He was not wholly at ease over the meeting.  The fact that Chauvenet had so promptly put a spy as well as the Servian assassin on his trail quickened his pulse with anger for an instant and then sobered him.

He continued his walk, and paused presently before an array of books in a shop window.  Then some one stopped at his side and he looked up to find the same man he had accosted at the Treasury Building lifting his hat,—­an American soldier’s campaign hat.  The fellow was an extreme blond, with a smooth-shaven, weather-beaten face, blue eyes and light hair.