At the time the sun set, although there was no telling when that was by looking at the sky, for it still rained, Louis found himself on picket duty for almost the first time in his life. He had often stood guard, but picket duty was different, for now it was positively known that the enemy was just ahead. He had been stationed close to the edge of a woods and was given a beat of twenty feet, ending on the right at a big oak and on the left at a sideroad running into the Yorktown highway. Next to him, at the other side of the oak, Harry was stationed, while Callings covered the road. The reserves, or companies sent forward to aid the pickets, if needed, lay in a hollow some distance back, and with these were several cavalrymen detailed for any messenger service which might be deemed necessary. Up and down his short walk tramped the young Union soldier, his gun loaded and his eyes and ears on the alert for anything which might appear in the least suspicious in the uneven field beyond the woods. He felt that he was now placed upon his mettle, and resolved that nothing should happen which might be put down to the enemy’s credit. Two hours went by, long hours to the youth, for the short beat soon became a wearisome one, and the pickets had been cautioned not to speak to one another unless it became necessary. Stopping now and then, he could hear Harry tramping up and down, and occasionally came a murmur from the roadway, as Callings forgot himself and started to hum some well known tune. And then, Louis stopped short again and clutched his musket tighter. What was that out in the field, moving slowly along beside a large, rough rock? With his heart standing fairly still, he dashed the rain from his eyebrows and took a step forward. Beyond a doubt it was the form of a man. CHAPTER XVII THE CAPTURE OF A SPY For the instant, after making his important discovery, Louis knew not what to do. That the fellow who was advancing so cautiously was an enemy there could be no doubt. That being so, why was the Confederate taking so much pains in the rain and darkness to enter the Union lines? There could be but one answer to this question. He must be a spy, bent upon some secret and important mission. As the truth forced itself home to the young Union soldier’s mind, he took a step in the direction of the roadway, feeling that the eyes of the man by the rock were upon him and that if he knew he was discovered it might prove a case of “who shot first” as to who remained alive to tell the story afterward. He must not show his hand until in a position to use his gun with quickness and accuracy. Turning from the roadway, he walked slowly back toward the big oak. As he did this he noted that the man had shifted his position and was now some six feet closer to the woods, where a low fringe of brush stuck up, and where the rain had formed a pool of shallow water extending a distance of several yards.