"It is queer," was the answer. "But if we have done anything like the damage to the Hun trenches that they have done to ours, it must be a bad place over there." "I think we've paid 'em back with interest," declared Jimmy. "Our gun fire was twice as heavy as theirs." And so it proved, for when dawn broke, gray and misty, it was seen that the line of German sand bags had been demolished for a long distance up and down the trench. And in the trench could be seen the German soldiers working frantically to repair the havoc. It was then that the Sammies could take revenge with rifle fire, and they did, in goodly measure. But no word came to go over the top, and a little while after day broke the firing died down on both sides. Soon it was comparatively quiet, but there were sad scenes to follow. The weather improved toward noon, and the sun came out to partially dry the muddy trenches and the rain-soaked garments of the soldiers. Bob's wound was dressed by a surgeon, and he was told to lay off duty for a day. Jimmy, too, had received a slight wound, and he had the same orders as had Bob. So the two of them went to the rear for a little rest. It was while taking such ease as they could that they saw an aeroplane land near the camp to which they had come to get a little respite from the fighting, and when they saw two figures leap from the machine, Bob and Jimmy exclaimed: "The Twinkle Twins!" It was John and Gerald Twinkleton. "Well, where'd you blow in from?" asked Jimmy. "Had to come down to get some gas, or petrol, as they call it over here," explained John. "Been out doing scout work. Say, I hear you had a hot time last night." "Sort of," admitted Bob. "Fritz tried to put one over on us." "Yes, we heard about it," went on Gerald. "And it came near being a bigger thing than you fellows suspect. Did you hear about the smoke signals?" "Smoke signals?" cried Jimmy. "Say, do you mean that there has been some more of that traitorous work going on?" "It looks so," said John. "When we were out flying around yesterday we passed over a little valley. We were low enough down to see four men around a queer kind of machine. At first we thought it was a hidden mortar battery, but soon we saw some green and yellow puffs of smoke go up from it. We reported the matter to headquarters, and there was an investigation right off, but the four men had disappeared with their smoke apparatus when a squad of our lads got to the valley." "Do you say there were four men around that smoke signaling apparatus?" asked Jimmy. "Yes," answered Gerald. "Could you tell who they were?" "Well, no, not exactly. Except that two of them seemed to be men in American uniforms, and the other two were civilians." "By Archibald Montmorency! as our cook would say," cried Jimmy, "I'll bet they're the same fellows we saw in the dugout. They are the traitors! This is great news you bring from the air, boys!" he said to the Twinkle Twins.