As he sat back on his haunches, to rub his head, Hal moved lightly forward, and, judging the distance by the sound of his enemy's movements, fell on top of him. He had gauged the distance to a nicety, and before the German could cry out, one of the lad's hands sank deep into his throat. But the latter was a powerful man and not to be overcome easily. He hurled the lad from him with a quick shove, at the same time twisting on the wrist of the hand that gripped his throat. The pain was almost unbearable and Hal was forced to loosen his hold. But again the lad sprang, before the German could take the offensive, and this time struck out fiercely with his right fist. The German uttered a cry of pain, and with one hand delivered a smashing blow at the face so close to his own. But Hal had figured on this move and had calculated the time of the blow perfectly. With a quick movement of his head he avoided the huge fist, and there came a terrific howl of pain from the German. The blow had passed over the lad's head and the German's fist had crashed into the solid wall. And at the same instant there came the sound of a shot from Chester's end of the cave. This sound spurred Hal to greater activity, for he realized now that their presence had been discovered by those on the outside. He felt certain that the sound of the shot would probably bring new visitors into the cave from the end he was supposed to guard. Quickly, then, while his opponent was still in agony from the self-inflicted blow, Hal drew his revolver and, reversing it, struck out in the direction of a muttered curse. He was rewarded by another groan of anguish and a moment later by the sound of a falling body. Quickly the lad leaped forward, his weapon held ready to strike again. But there was no need of a second blow. The German was unconscious. By great exertion Hal succeeded in turning his wounded adversary over and pushed him slowly along the passageway, using him as a shield in case he encountered another of the enemy. At length he came to the end of the passageway, and pushed his prisoner out. Even as he did so a bullet whistled by his head and he heard the crack of a German rifle. Hal lost no time in getting back into his hiding place. But now he discovered that even this was not far enough, for a bullet came whizzing into the cave after him. It hit the side of the wall and went skimming over his head. With all possible haste the lad retreated around the little bend, and throwing himself upon his face held his revolver ready to fire at the first sign of an advancing foe. He lay perfectly still, not making the slightest noise, and after some moments heard the sound of voices. "I tell you I must have hit him. I never miss at that distance," said one. "And, besides, if he were in there we could hear him." "I wouldn't be too sure," came a second voice. "He's liable to be there waiting for you." "Well, I am going in after him anyhow," said the first speaker.