Posting his fifty sentries about three hundred feet apart the Army boy thus covered a stretch of water-front some three miles in length, the village's strip of river front being nearly at the middle of this line. Corporal Smith's patrol was at the westerly end of the line. Hal himself headed the patrol at that end. The sentries were instructed to conceal themselves, in order to catch, if possible, any band of rebel smugglers in the act of loading war munitions on a craft. "Nothing will come of it to-night," muttered Hal to himself, after he had placed his men. "The Mexicans here know that there are troops on the spot. If they were going to ship guns to-night they'd be sure to do it at some point ten or twenty miles from here. This is a job for a whole brigade of infantry. A regiment of cavalry could do more than three regiments of infantry on this work." But Hal knew that the only two troops of cavalry so far ordered to frontier patrol were two troops at least a hundred miles to the westward. As yet Uncle Sam's soldiers were posted only at particular points known to harbor resolute Mexican rebels. "The fish can get through the net without the least trouble," thought the young officer. It was still, dark and quiet out here on the river front. There were no lights, and seemingly none astir except the soldiers. "Corporal, you stay with the patrol. I'm going to do a little exploring on my own account," said Lieutenant Hal, after another hour had passed. "Very good, sir," replied Corporal Dent. Hal had no very definite objective when he started off eastward by himself. He had left his sword behind in camp, but his revolver rested in its holster on his right hip. The more Lieutenant Hal thought about it the less he was inclined to feel that there was any likelihood that Mexicans would attempt to-night to cross the river anywhere in the neighborhood of United States troops. "The leaders among these fellows all know that they're being watched," thought Hal, "and they won't take chances when success means so much to them. Now that the troops have come Guarez and his associates will take time to think this matter over. None the less I shall have to be as vigilant as though I knew that they meant business to-night. It would be a fearful black eye on my record as an officer, right at the start, if I allowed the Guarez crowd to get anything real over the river to-night." As he strolled along the water front the young lieutenant passed one of his sentries every few hundred feet. Part of the Army boy's purpose in going along by himself was to make sure that each and all of his men were alert. Their vigil would last until daylight.