Roque was not puzzling about the appearance of the dancing light; it was the message that it conveyed which baffled him, sent, as it were, from within the German lines, and, maybe, of vital concern--aid and comfort to the enemy. Sentries on the heights had reported night after night of this queer, intermittent flashing in this very place, and when Roque heard of it, he instantly comprehended the meaning. Some spy within the lines was using a luminous kite to signal information of value to the foe. This is what had brought the secret agent, an adept in the same kind of game, flying through the night to scotch the play and the player. Roque and Schneider skirted the ruins, and stumbled over the plowed ground with all the haste that such rough going permitted. The boys, free of any order to stay where they were, cautiously brought the rear. They were mighty curious to see what was going to happen. Schneider had taken the electric torch from under the pilot's seat in one of the biplanes, and it had occurred to Billy to follow suit. This precaution served to save the party an ugly tumble or two into forbidding ditches. The still-hunters had just emerged into a road with a wonderful avenue of trees. The kite telegrapher's hidden nest was near at hand. The position of the kite itself indicated that. A streak of moonlight breaking through a cloud-rift revealed Roque and Schneider kneeling in the road, and there was a glint of a leveled rifle barrel. The boys backed up against a tree, expecting momentarily to hear the whip-like crack of the gun. But instead came the bark of a dog--one shrill yelp, then silence again. The luminous kite, unleashed, followed the moon into the clouds. Roque and Schneider dashed forward, but for nothing else than to use the electric torch in locating a half-loaf of bread, some cheese crumbs and a ball of cord. The sentry dog had saved its master! "Nothing to be gained in chasing that fox to-night," growled Roque. "He's deep in the brush before this." "I'd like to have got a pop at the dog, at least," complained Schneider, patting the stock of his rifle. The boys having no desire to be the victims of any mistake of identity, marched forward, Billy waving the electric torch, and calling to Roque: "It's us." The passwords were unnecessary, for Roque knew all the time the boys were trailing him, but was restrained from objecting by fear of some word reaching the ear of the man they were stalking. "You gadabouts," he admonished, "you should have been guarding the biplanes instead of prowling around in the dark like this." The tone of the reprimand, however, was not one of great severity. The boys had disobeyed no order, for none had been given. "As soon as day breaks," said Roque, as they plodded wearily down the road, "we will continue the hunt in the machines, though I doubt very much whether it will amount to more than a waste of time."