"Good-bye, my young friends, and good luck to you; if you ever see Colonel McCready again tell him 'here's looking at him.'" These were the parting words of Colonel Muller, accompanied by a warm hand-grip. When the flying party finally reached Strassburg, the big German city of the Alsace-Lorraine region, it was a glad day of halting. They had floated in over a country literally shot to pieces by the concentrated fire of the French and German guns--that is, in French Lorraine--and in the distance viewed the great fortress of Metz. To the aviators it appeared as though the land hereabouts had been devastated by a gigantic earthquake, which had shaken down all the towns and villages into a mass of shapeless, smoke-blackened ruins. The boys wondered that they did not see more soldiers in the open, and Henri expressed this wonder to his companion in the biplane. "Oh, but the woods are full of them," assured Schneider, pointing to the small columns of smoke rising here and there from the snow-clad forests. True it was that these same woods contained thousands and thousands of armed warriors, ever on the lookout, who were gazing across the frontier at the other woods, which concealed countless thousands of soldiers of the Kaiser. In Strassburg, Roque was again in touch with the invisible strands of the far-spreading web he maintained. Among his first advices was the most disturbing one that Ardelle had returned and had been making some ten-strikes within the borders of the empire. The boys shrewdly guessed that something of the sort had happened from the renewal of the German agent's habit of charging almost every sort of disaster to the secret work of his French rival. Roque realized, as one of the profession, what an important factor is the under-cover man who works within the enemy's lines in the service of his country. And with a keen blade like Ardelle, big things were possible, as past performances indicated. But even Henri, as a self-claimed prophet, had no idea that the man he knew as Anglin would bob up in Strassburg, though the city was as likely a point as any in the war zone for secret service activity. When Billy jokingly asked his chum if he had any predictions to fit this occasion, Henri admitted that his second-sight "was off the job." It soon developed that the secret service experts of both sides were matching wits in this quarter. Reported in Roque's calendar of the week was the giving away by one of his workers in hostile territory of a French attack on the Germans during a fog, with the result that the intended surprise resulted in a rout, and the assailing force mowed down almost to a man. The mute testimony was in a low-lying valley out in the Lorraine field--700 graves in a space 200 yards wide and about 50 broad.