"Must be deserted," he finally remarked. "Such being the case, lieutenant, I reckon I might as well take possession." "Sure. Go ahead. If every one has gone, I may join you later." Billie led his horse within and looked around. It was a large house and the patio was the most elaborate Billie had ever seen. He had thought that Pedro's home in Mexico City was fine, but this was much finer. "They must be swells," was the lad's comment. "I reckon they became frightened and have run away with General Maas." He started to lead the horse to the stable and then stopped. "I might as well shut this big gate," he thought. "I'll leave the little gate open so the lieutenant can come in." He pushed the big gate together and dropped the bolt in its place. "Now to do something for the horse," and he turned to the animal which stood patiently by. Then he stopped and stood in mute astonishment at what his eyes beheld. In the center of the patio, with rifle in hand, aimed squarely at his head, stood a figure he had last seen on the banks of the Rio Grande more than a year before--the figure of a man whom he had known only as Santiago. The recognition was mutual, but instead of the friendliness which had always before marked the attitude of the strange man, there was now upon his face a look of the most bitter hatred. CHAPTER XVI. SHADOWING AN ARMY. When Donald and Adrian left the city they rode slowly along for some distance without any sign of the retreating Mexicans, except the occasional sight of some camp utensil which had been thrown aside as too heavy to carry. Occasionally they met peons or women, who looked at them curiously, but all of whom were more than willing to tell of the army that had so recently passed. "How many men do you suppose General Maas has?" queried Adrian. "The lieutenant said it was supposed he had about seven thousand. It may be more, and it may be less." "Well, they're certainly light-footed," laughed Adrian. "Don't you think we ought to get closer?" "If we can without being seen." They put spurs to their horses and for a mile or more galloped along at a fair speed. Then from a little eminence they saw the rear guard of the retreating army. "This is near enough," cautioned Donald. They halted and watched the marching men. "How far would you say we are from town, Don?" "At least seven or eight miles." "Do you know what towns are in this direction?" "Not the slightest idea. That's the next thing we must find out." The enemy having by this time passed out of sight, they again spurred forward, but holding their distance. Darkness had now fallen and the boys were obliged to pick their way more carefully. For half an hour they rode silently and then Donald spoke: "They certainly will not march all night. They must have some place in mind." "So I think," from Adrian. "But there seems no sign of a halt." Ten minutes later, however, they caught sight of a fire light.