Wonderingly the four gazed at one another. CHAPTER XIII A FORWARD RUSH "There's a lot more to this than any of us suspect, I guess," said Gerald Twinkleton, with a grave shake of his head. "Of course when Jack and I saw those men sending up smoke signals we didn't dream, at first, that anything was wrong. But when we noticed the two civilians with them we guessed there must be some queer deal on, and we decided to report matters. Then we learned that this wasn't the first time those signals had gone up, and each time, after they had shot up into the air, there was an enemy attack." "Bad business," commented Jimmy. "But if those fellows are spies, including the two in uniform, where would they get one of our smoke-making machines?" asked Bob. "The signal corps has a number of them," explained Jimmy. "One might easily be stolen, together with the chemicals needed." "The signal corps!" cried Roger. "And those Bixtons--who are off the same piece of goods as Mike, back at Camp Sterling--those Bixtons are in the signal corps!" "That's what makes me say there's more to this than appears on the surface," commented Gerald. "Now let's hear again what it was you saw in the dugout, Jimmy boy." Thereupon Jimmy related what they had seen as they were making their escape after the collapse of the shelter where they had been resting. "Would you say for sure that the two you saw in uniform in the dugout were the two Bixtons you afterward noticed in the signal corps?" asked Jack of Jimmy. "No, I couldn't be positive," was the answer. "You see we didn't have more than a hasty glimpse of them, and then only by the light of a candle. But from what you Twinkle Twins tell us, it's evident that the same four--two in uniform and two without--who were in the dugout were also sending up smoke signals." "Well, it looks that way," admitted Gerald. "Of course, there's always a chance that things may take a different turn, but there's enough here for headquarters to get busy on." "The main thing to do, in my opinion," declared Jimmy, "is to find out if the fellows we saw in uniform in the dugout and the two the Twinkle Twins saw sending up signals are the same, and then to learn if they're the Bixtons." "That's the idea!" exclaimed Bob. "But it's easier said than done." "We'll help all we can," said the Twinkleton Twins, as they started off again in their aeroplane, the tank having been filled with gasolene. The secret service men at headquarters, including Captain Frank Dickerson, at once acted after the boys had given the additional information in their possession.