“Show your authority,” said Frank, taken a little aback. “Let go his arms, fellows.” His arms released, the man threw back his coat and showed the badge of his service. “I’ve been trailing this man for some time,” he said. “We had a suspicion that he was in treasonable relations with the enemy. And I think now I’ve got the goods on him,” he said, as he flourished the bundle of papers. Here the old man interposed. “It’s false,” he cried wildly. “No one is more loyal than I am. Look at those papers. Look quick or it may be too late. The Germans plotted to blow up the fortress of Ehrenbreitstein, if it were ever captured by the Americans. Those are the plans. By an oversight of theirs, the papers fell into my hands. I hid them here when I had to leave Coblenz. I did not dare to take them with me for fear I would be searched. That was why I wanted to get back to Coblenz, so that I could give the papers to the American commander. I have been sick, delirious since I returned, and this is the first time I have been able to leave my bed and get here. Look at the plans. And hurry, hurry!” There was unmistakable sincerity in his tones that startled and impressed even the Secret Service agent. They hurriedly examined the plans. Two minutes sufficed. Ehrenbreitstein, where at that moment thousands of American soldiers were sleeping, might at any moment be blown into atoms! Two jumps carried Frank out of the cellar. A few more took him to a telephone. There was a quick exchange between him and the fortress. Then the whole party bundled themselves into a car which had been hastily commandeered and were whirled over the bridge and up the hill. A few minutes more, and squads of soldiers, armed to the teeth, had followed the indications of the plans and located enough explosives in a secret passage deep under the fortress to shatter it to fragments. The wires by which they could have been exploded from a distance were found and severed, and only then did the commander of the fortress, who had lived ten years in as many minutes, venture to breathe freely. The bold plot of a desperate band of Germans had been foiled. But other plots were still to be exposed, and what some of those were will be related in the next volume of this series, to be entitled: “Army Boys on German Soil; Or, Our Doughboys Quelling the Mobs.” In that book we shall meet all our friends again and see how bravely they acted under the most trying of circumstances. “It was a narrow squeak,” remarked Frank, a few days after the German plot had been exposed. “Just what I was saying to Helen this afternoon,” said Billy. “And what were you saying to Alice?” asked Bart, turning to Tom. “None of your business,” grinned Tom. “They’re hopeless cases,” remarked Bart. “Cupid’s got the best of them,” remarked Frank. “That’s more than the Huns could do,” laughed Billy.