If Don Carlos had only known where his missing guest was all this while, and what he was doing, and what he was seeing, he would have had good cause for alarm. Archie was not at home, as Frank fondly hoped, nor was he outside the rancho. He was in a worse predicament than he had ever been in before, and was learning some things about Don Carlos and his house that greatly astonished him.

We said that the last time Frank saw him, he was standing before a large oil-painting in the room where the Spaniard had left them. It was a life-size picture of an Indian warrior; and so well was it executed that, as Archie stood looking at it, he almost expected to see the savage open his lips to give the war-whoop, and then draw the bow which he carried in his hand, and discharge an arrow at him.

“The man who painted that was an artist, and understood his business,” said Archie, to himself. “I have seen lots of those fellows, and that’s just the way they look.”

Something in the picture, which he had not before noticed, caught his eye at this moment, and interrupted the thread of his soliloquy. The handle of the warrior’s hunting-knife, which he wore in his belt, was rounded off into a knob at the end, and Archie was sure that it stood out a little way from the canvas. He leaned forward and looked at it more closely, and sure enough it was a wooden button, which fitted into the end of the handle of the knife, and not a painted one. He stepped up and examined it with his fingers, and to his surprise it yielded to his touch.

“Now I’d like to know what this means,” thought he, pressing the knob harder than before. “This thing must be attached to a spring, because it comes back when I let go of it. Well—by—gracious!”

It was very seldom indeed that Archie used any slang words, but sometimes, when he was greatly excited or astonished, he did like other boys—forgot all the good resolutions he had made regarding this bad habit. It was no wonder that he was amazed now, for the painting began to move as if it had been suddenly endowed with life. It opened before him like a door, swinging swiftly back on a pair of invisible hinges, and revealing a narrow, winding stairway which seemed to run down into a cellar beneath the outer wall. Archie stood like a wooden boy for a few seconds, his neck outstretched, his eyes dilating and trying to pierce through the thick darkness which enveloped the stairs, and then, scarcely knowing what he was about, he stepped cautiously into the passage. An instant afterward he would have given every thing he possessed, or ever expected to possess, if he had been a little more prudent; but then it was too late. The painting swung back to its place as swiftly and noiselessly as it had opened, and the smooth click of a spring-lock told Archie that he was a prisoner. He did not intend to remain one long, however. He understood the mystery of that secret door, and it would not be many seconds before he would get out again. Perhaps Frank would now be willing to look up from his book long enough to hear him tell of this wonderful discovery he had made; and perhaps, too, he would be ready to believe that he had some foundation for his suspicions.

Talking thus to himself, Archie groped his way back to the painting (for now that the opening was closed the passage was as dark as midnight), and began to pass his hands over it, searching hurriedly for the concealed spring. He now found that the back of the picture was formed of heavy oak planks, nearly a foot in thickness; or, to make the matter clearer, the whole contrivance was simply a ponderous door, with the painting spread over one side of it to conceal it. But where was the spring? Archie ran his fingers over every inch of the door, from top to bottom, but could not find it. He examined every one of the planks separately, and finally turned his attention to the huge blocks of stone which formed the walls, in the hope that he might find the spring imbedded in one of them. Five minutes—ten minutes—a quarter of an hour were passed in this way, and then Archie sank down upon the floor, all in a heap, panting and sweating as though he had been engaged in the most violent exercise. His face was very pale, his hands trembled as though he were suffering from an attack of the ague, and one to have seen him at that moment would have believed that he was almost overcome with fear. His words, however, did not indicate the fact.

“Now here’s fun,” said he, with a desperate attempt to keep up his courage; “here’s sport—here’s joy by the wagon-load. I am cornered easy enough, and it serves me just right for prying about where I had no business. What will the Don say when he comes back and finds me gone?”

As this thought passed through Archie’s mind, he sprang to his feet, the cold perspiration starting out anew from every pore in his body, and his heart beating fast and furiously. What would the old Spaniard think when he found that one of his guests was missing, and, above all, what would he do? If he was an innocent man, and Archie’s suspicions regarding him were without any foundation, he would hunt him up and release him; there would be a hearty laugh all around; and the Don would have a long story to tell about the passage-way, the reasons why he had built it, and the use he had made of it. But suppose that Archie’s suspicions were correct—that Don Carlos was really one of the robbers, and that the passage led to some underground cavern where he and his men concealed their plunder—what would he do when he found that his secret had been discovered? Archie did not stop to answer this question, but once more searched all over the door for the spring; but with no better success than before. Then he pounded upon the door, and called his cousin; but the walls were thick, and the sound of his voice did not reach Frank, who read on in blissful ignorance of what was transpiring on the other side of the painting.

“He must have gone out,” said Archie, now beginning to be thoroughly alarmed, “and I am left to my own resources, which are scarce, I can tell you. What if one of the band should come up here with a light?”

Archie pulled his revolver from his pocket, faced about, and peered through the darkness in the direction of the stairs, listening intently, and almost imagining that he heard light footsteps approaching. But he was alone in the passage-way, and having satisfied himself on this point, he leaned against the wall to think over the situation, and determine upon some course of action.

“It would be awkward to be caught here—for the robber, I mean, for it is my opinion that he would go down those stairs with much greater haste than he came up. Of course there must be two ends to this passage, and as I can not get out here, I must try some other way of escape. I can’t be in a much worse fix than I am now.”

As Archie said this, he put his revolver into his pocket again, and began feeling his way along the wall toward the stairs. It was a dangerous undertaking, for the floor might be full of trap-doors, for all he knew, and one of them might open beneath his feet at any moment, and let him down into some dungeon; or, he might run against one of the robbers in the darkness, who would slip a lasso around his neck, and make a prisoner of him before he could raise an arm to defend himself. He reached the head of the stairs, however, without any such misfortune, and slowly and cautiously felt his way to the bottom. There he found himself in a passage-way which ran at right angles with the one above. After a moment’s deliberation, he decided that if he followed it to the left it would lead him under the court (through which Frank was, at that very moment, running a race with Pedro for the gate), and that was the way Archie did not want to go. By turning to the right, if the passage ran far enough in that direction, he would reach the bank of the creek, and there he might find some way of escape. Having decided this point, he was about to move on again, when he was frightened nearly out of his senses by hearing a whisper close at his elbow:

“Beppo, is this you?”

The fight for which Archie had been bracing his nerves ever since he first made up his mind to visit Don Carlos’ rancho, was to come off now—he was sure of that. He was much calmer than he had thought he could be under such circumstances, but still he trembled violently in every limb as he drew his revolver, and thrust it straight out before him in the direction from which the voice came. A person thinks rapidly when in danger, and during the moment’s pause that followed the question thus unexpectedly propounded to him, Archie thought over and rejected a dozen wild schemes which suggested themselves to him. One, however, he accepted. He would reveal himself to the man, and if the latter would agree to show him the way above ground, it would be all right; he would then be willing to believe that Don Carlos was an honest man, and that there was nothing wrong about him or his rancho. But if the man made an outcry, and began shouting for help, or tried to secure him, he would give him some idea of American pluck and muscle.

“Beppo, is that you?” asked the voice again, in the same cautious whisper. Then, before Archie had time to act on the resolution he had just formed, the man, whoever he was, continued: “here are the keys. We shall be ready in half an hour. Follow this gang-way, and enter the first door on your left. Be sure and lock the door after you, because there’s always somebody roaming about here, and you might be discovered. Do your work well, now, and the revolver is yours.”

A moment afterward Archie stood holding a bunch of keys in his hand, and listening with beating heart to the retreating footsteps of the man, who was hurrying toward the other end of the passage. He had never been more excited and alarmed in his life. If the man had brought a lantern with him, the fight he had been expecting would certainly have come off.

When the sound of the footsteps had died away, Archie drew a long breath of relief, and began to congratulate himself on his escape, and to repeat what the man had said to him. Two things were evident: one was that he had been mistaken for Beppo, a Mexican boy about his own age who was employed on the rancho; the other, that he had some sort of a secret commission to execute, and that for the faithful performance of his work, he would be rewarded by the present of a revolver. What that commission was, Archie neither knew or cared; he had something of much more importance to think about. Suppose the man should happen to meet the genuine Beppo, and should find out that he had given the keys to somebody else! Would he not try to ascertain who that some one else was, and wouldn’t he call for help, and begin a thorough search of the rancho?

“I haven’t a single instant to lose,” said Archie, to himself. “Let me see! I must follow this gang-way and open the first door on my left, and be sure and lock it after me. I don’t much like to do it, for there is no knowing what I may find in that room. I hope one of these keys will let me out of this den of robbers.”

So saying, Archie began to feel his way along the left wall of the passage, and presently came to the door of which the man had spoken, and which he succeeded in opening after trying several of his keys. Hastily passing through the door, he closed and locked it, and then began to feel a little more secure; although he did not know which way to turn next. If he kept straight ahead, he might come in contact with some object, or step upon one of those trap-doors he so much dreaded. After a little hesitation he placed his hands upon the wall, and began moving slowly around the apartment, but had not taken more than half a dozen steps before he ran against something. A moment’s examination showed him that it was a table, with several articles upon it—a bowie-knife, a brace of pistols, two or three lassos, a lantern, and a box of matches. These last were just what he had been wishing for. He lighted the lantern, and then turned to take a survey of the room. It proved to be a sort of armory and depot of supplies. The walls were covered with weapons, and saddles, bridles, blankets, ponchos, and numerous other articles of like description, were scattered about over the floor. A hundred horsemen could have been equipped from that room.

As soon as Archie had satisfied himself that he was alone, he began to examine the objects about him a little more closely; and almost the first thing his eyes rested on was a piece of property belonging to himself.

“Isn’t it lucky that I didn’t speak to that man?” he soliloquized. “Didn’t I say that old Spaniard was one of the robbers? That’s my saddle. I would know it among a million. It is the very one that was on Sleepy Sam when Uncle James bought him in St. Joseph. Now, my horse is in this very rancho; and he isn’t far off, either. This settles the question of Don Carlos’ guilt.”

Archie now became doubly anxious to effect his escape from the rancho. The man who had given him the keys had told him that some one was always roaming about those passage-ways, and as long as he remained there he was in danger of discovery. But he had said that if his horse was in that rancho, he would have him out, and he was going to keep his word. He would not think of going home until he had found him. Once on his back, and outside of the walls of the rancho, he could laugh at the robbers. If Roderick was there, he would take him, too. He hoped to be able to secure both horses, and make good his retreat without being discovered; and if he could do that, wouldn’t he astonish his cousin when he came home in the morning? But something prevented Archie from carrying out this plan. As it happened, Frank was the one who recovered the horses; and if it had not been for him and Roderick, Archie would never have mounted King James again.

Archie’s first care was to take possession of the weapons he found on the table; then he raised his lantern, and took another survey of the room. He saw a door opposite to the one by which he had entered; and when he had opened it, he found that it led into a long, low apartment, which was used as a stable. It contained several horses, which the robbers had selected and kept on account of their great speed and endurance, and conspicuous among them stood Roderick and King James.

“Aha!” exclaimed Archie.

“Santa Maria!” cried somebody else.

Archie looked up, and there was Beppo. His mouth and eyes were wide open, and he stood gazing at the intruder as if he could not quite make up his mind whether he was a solid flesh-and-blood boy, or only an apparition. The fight must come off now, and Archie was ready for it.