The fervor of the singer did not decrease, but Harry noticed that he too was moving, moving slowly toward the eastern end of the grove, the same direction that Harry was pursuing.  Now he was sure.  He would have called out, but his voice would not have been heard above the vast volume of sound.  He might have pointed out the singer to others, but, although he felt sure, he did not wish to be laughed at in case of mistake.  But strongest of all was the feeling that it had become a duel between Shepard and himself.

He walked slowly on, keeping the man in view, but Shepard, although he never ceased singing, moved away at about the same pace.  Harry inferred at once that Shepard had seen him and was taking precautions.  The temptation to cry out at the top of his voice that the most dangerous of all spies was among them was almost irresistible, but it would only create an uproar in which Shepard could escape easily, leaving to him a load of ridicule.

He continued his singular pursuit.  Shepard was about a hundred yards away, and they had made half the circuit of this huge congregation.  Then the spy passed into a narrow belt of pines, and when Harry moved forward to see him emerge on the other side he failed to reappear.  He hastened to the pines, which led some distance down a little gully, and he was sure that Shepard had gone that way.  He followed fast, but he could discover no sign.  He had vanished utterly, like thin smoke swept away by a breeze.

He returned deeply stirred by the appearance and disappearance—­easy, alike—­of Shepard.  His sense of the man’s uncanny powers and of his danger to the Confederacy was increased.  He seemed to come and go absolutely as he pleased.  It was true that in the American Civil War the opportunities for spies were great.  All men spoke the same language, and all looked very much alike.  It was not such a hard task to enter the opposing lines, but Shepard had shown a daring and success beyond all comparison.  He seemed to have both the seven league boots and the invisible cloak of very young childhood.  He came as he pleased, and when pursuit came he vanished in thin air.

Harry bit his lips in chagrin.  He felt that Shepard had scored on him again.  It was true that he had been victorious in that fight in the river, when victory meant so much, but since then Shepard had triumphed, and it was bitter.  He hardened his determination, and resolved that he would always be on the watch for him.  He even felt a certain glow, because he was one of two in such a conflict of skill and courage.

The meeting having been finished, he went down one of the streets of tents to the camp of the Invincibles.  Colonel Leonidas Talbot and Lieutenant-Colonel Hector St. Hilaire were not playing chess.  Instead they were sitting on a pine log with Happy Tom and St. Clair and other officers, listening to young Julien de Langeais, who sat on another log, playing a violin with surpassing skill.  Lieutenant-Colonel St. Hilaire, knowing his prowess as a violinist, had asked him to come and play for the Invincibles.  Now he was playing for them and for several thousand more who were gathered in the pine woods.