And it was no easy task which his duty set him. Over sharp rocks and through tangled briers that black line led him on. Sometimes the moon would desert him and he would lose the clue for a while. Sometimes he would be forced to abandon his clue to skirt around an insuperable barrier. But he always came back to it, always pressed on. On and on! And then, suddenly, the line disappeared. It ended, or seemed to end in a large pile of boulders which clung to the mountainside. The undergrowth was dense here. Danny circled about the spot. Yes, the wire stopped here. He began creeping through the underbrush--feeling his way along the side of a great boulder. Suddenly his hand touched--_nothing_! The scout stopped and thought. There was some sort of break in the rock here. Danny had a flashlight in his pocket which he had been too cautious to use. He thought of it now, and hesitated. Then he slipped it out and pressed the spring. Before him was what seemed the door of a cave. He looked closer. Yes, the wire led into the cave. Darkness, again, for he was afraid to use his light any longer. Danny dropped to his all-fours and crept into the black hole. A floor of soft sand helped him to advance noiselessly. After a few yards the scout reached a turn in the rocky passageway, and---- His eye caught a big, black-hooded shadow humped over a point of light! Danny withdrew quickly behind the sheltering turn in the wall, and crouched in the sand, dead-still. But his blood was up. He took a second look. A man was sitting over some sort of instrument, and over his ears were cups, something like Danny had seen worn by the girl at the telephone central station. The one point of light in the big dark recess was turned on a note-book under the man's hand. The young scout drew back, and crept silently out of the cavern. Out under the stars again, and this time with his blood on fire! A spy, a German spy sat in that cave and sent messages----! Only yesterday a fleet of transports had slipped out of the harbor, with thousands of American soldiers on board--submarines--sea-raiders! But a scout must keep his head. Help? Which way could help be found? The boys were scattered, McKenzie would not be in camp. Nobody knew when to expect Mr. Gordon. Which way? Which way? Oh, yes, down over the drop of the cliff to the south yonder was the mountain wagon road by which their scouting party had ascended that afternoon. If he could get to the road he could find somebody somewhere--surely, there were a few inhabitants hereabouts! That German was sending wireless messages right this minute---- Yes, the shortest way to the road was the only way for a fellow to take now! And Danny took it.