“Hello!” exclaimed Tom suddenly, in a note of new surprise, and an instant later the far wall flung back the word at them as though someone there were repeating it in mockery. There was something unpleasant about the situation. It was like wandering around aimlessly in the dead of night in an abandoned house reputed to be haunted, not knowing what startling surprises awaited one at any moment. Tom’s exclamation escaped him when he noticed that the tunnel apparently came to a dead end about twenty-five feet ahead. A moment later, however, it was apparent they were approaching a right-angled turn. Tom extinguished his own light to see if any ray came from down this new passageway, but there was nothing but pitch blackness, in which neither lad could discern the outline of the other. Snapping it on again they proceeded slowly until Tom stood within a foot of the abrupt turn in the wall. The new tunnel ran directly to the right of the direction in which they had been approaching. With a sudden forward thrust of his head, Tom took a quick survey of what lay beyond. He drew back with a gasp, and his free hand fell upon Harper’s arm. “Look!” was all he could say for the moment, and Harper, following Tom’s bidding, drew in his breath sharply, then gave a low whistle. They had made a discovery of tremendous moment! But had they made it in time? “Out! Out!” Tom ordered. “We may be blown to atoms any second if we stay here.” And indeed it was true. The sharp turn in the tunnel brought them into a great cavernous chamber in which there must have been at least fifty tremendous bombs, all connected by copper wires with a heavy cable which hung suspended from the ceiling. It was obvious that during their long occupancy of the St. Mihiel salient the Germans had dug this tunnel and planted these mines, for just such a contingency as now existed—enemy occupation of Thiaucourt. And while neither lad was an engineer, both knew sufficient about bombs to realize that there were enough there to blow the whole town site off the map and annihilate every person within a radius of more than half a mile. “Ten thousand men are quartered on the space that those bombs would blow up, and the Germans may touch them off at any time! Run! Run!” Tom ordered, and, setting the example, he bounded by Harper, the searchlight held out before him, tearing toward the mouth of the tunnel as fast as his legs would carry him. “They’re probably waiting for that German lieutenant to return,” Tom managed to speculate jerkily, without in the slightest reducing speed. “It’s pretty clear now that he was down here—to see that everything was all right—and put on—finishing touches.” “Yeh,” agreed George, “and it just occurs to me now that he wore the insignia of the Signal Corps.” “Wanted those papers,” Tom supplemented, “so as to know when the largest number of our men would be over the spot.”