"They were Spaniards who made this clearing and built this fort," he explained to his chum. "It may have been part of one of DeSoto's expeditions, or they may have been one of the treasure-hunting parties that were so numerous in the fifteenth century. Likely they became disgusted with tramping through swamps, and, when they came to this pleasant spot, they decided to stay for a time at least. So they, probably, made captives of many of the Indians, and put them to work, clearing, planting and building. But the Indians had their revenge in the end." "You can stay here as long as you want to, but I am going to get out in the fresh air," said Walter, shuddering as he watched a hairy rat creep out from one of the suits of armor. "I will wait for you just outside the fort." "All right," Charley agreed. "I'll be out in a few minutes." Left to himself, the lad searched around in the corners for a few minutes, trying to find something to carry away with him as a souvenir of their strange discovery, but, finding nothing, he soon gave up the hunt, and, gathering up his game bag and gun, he made his way back down the stairs and out of the fort, glad to be in the sunshine and fresh air once more. Walter was not in sight, and, after calling him a couple of times, Charley decided that he had probably grown tired of waiting, and had returned to the orange trees to eat his fill, and for them the lad hastened. But his chum was not there, and, with a vague feeling of alarm, the lad hurried on to where they had left their ponies, but Walter was not there. Now thoroughly alarmed, the lad fired off his gun four times in rapid succession, then waited and listened, but there came no answering report. After a moment's consideration, Charley turned around and hastened back to the ancient clearing. He made the round outside of the stockade, and then, entering the gate, searched the inside thoroughly, but no sign could he find of the missing one. Again he fired the distress signal of four shots, but there was no reply. The thoroughly frightened lad sat down on a block of stone, and strove to master his nervous fears and gather together his scattered wits. The whole thing was incomprehensible. Not fifteen minutes had elapsed since he had parted with Walter in the upper chamber of the fort, and now his chum was gone. He could not have gotten lost in the woods, for the way back to the ponies could be followed by a child, with its plain landmarks of orange trees and the other clearings. Besides, in that short length of time, Walter could not have got beyond the sound of the gun signal, to which he would certainly have replied. CHAPTER XX. THE HIDDEN VOICE.