There was something in the tone of that awful voice that increased the ape-man's curiosity. He guessed from the volume of the sound that it must come from the throat of a tremendous beast, for the very hills seemed to shake to the thunder of its roars. Guessing that it was attacking or was about to attack some other creature, and spurred, perhaps, entirely by curiosity, Tarzan hastened forward at a brisk trot, and as he rounded the shoulder of a buttressed crag his eyes took in a scene that galvanized him into instant action. A hundred feet ahead the trail ended at the mouth of a great cave, and in the entrance to the cave stood a boy--a lithe, handsome youth of ten or twelve--while between the boy and Tarzan a huge cave bear was advancing angrily upon the former. The boy saw Tarzan and at the first glance his eyes lighted with hope, but an instant later, evidently recognizing that the newcomer was not of his own tribe, the expression of hopelessness that had been there before returned to his face, but he stood his ground bravely, his spear and his crude stone knife ready. The scene before the ape-man told its own story. The bear, returning to its cave, had unexpectedly discovered the youth emerging from it, while the latter, doubtless equally surprised, found himself cornered with no avenue of escape open to him. By the primitive jungle laws that had guided his youth, Tarzan of the Apes was under no responsibility to assume the dangerous rôle of savior, but there had always burned within his breast the flame of chivalry, bequeathed him by his English parents, that more often than not found him jeopardizing his own life in the interests of others. This child of a nameless tribe in an unknown world might hold no claim upon the sympathy of a savage beast, or even of savage men who were not of his tribe. And perhaps Tarzan of the Apes would not have admitted that the youth had any claim upon him, yet in reality he exercised a vast power over the ape-man--a power that lay solely in the fact that he was a child and that he was helpless. One may analyze the deeds of a man of action and speculate upon them, whereas the man himself does not appear to do so at all--he merely acts; and thus it was with Tarzan of the Apes. He saw an emergency confronting him and he was ready to meet it, for since the moment that he had known that there was a beast upon the trail ahead of him he had had his weapons in readiness, years of experience with primitive men and savage beasts having taught him the value of preparedness. His grass rope was looped in the hollow of his left arm and in the fingers of his left hand were grasped his spear, his bow and three extra arrows, while a fourth arrow was ready in his right hand.