Without a word, Billy returned the paper to the heaver. The officer of the day was approaching. He signed the delivery receipt, but the paper had queerly changed color in the handling. As the lads slowly walked toward aviation headquarters their minds were all in a whirl. Prisoners they were and prisoners they had been, yet in both instances it had been but the semblance of captivity. While they were held, the rein had been a loose one. Just back of them the ties of long association, immediately in front of them a trust imposed, a generous parole, when they had gone to the limit in giving the best of themselves, in the one capacity they could serve, to the former rule. Thursday evening at eight, and this was Tuesday evening at six. Long enough, indeed, for the boys to torment themselves with the reflection that if they did not appear at the appointed hour Roque and Schneider would curse their perfidy, and if they did betray the confidence of the aviation chief in this camp he would pay the penalty. "It will be no trick at all to take the biplanes for an evening spin; we have done it before without question." "That's the trouble, Henri", lamented Billy, "it's too easy. If we had to steal the machines, risk our lives before the guns of the sentries, and all that sort of thing, it wouldn't seem such a trial of conscience. But they take us on trust, and without question." "Yet, here's Roque and Schneider in the lurch, and looking to us for aid. With them we have met about all that is coming to a fellow in this war zone, except death, and pretty near that; we have eaten and slept and starved together." "There you are again, Henri, and it's 'twixt the devil and the deep blue sea!' any way you put it." Thursday morning, and as clear as a bell. The Boy Aviators looked red-eyed on the smile of nature. Their cots had squeaked protest all through the night against the tossing of the uneasy nappers. At noon they had about made up their minds to keep the appointment at Two Towers, and seeking to strengthen this resolution they avoided in every way they could meetings with the aviation chief. Along about three in the afternoon the wavering youngsters had arranged a compromise, this to be positive. They would deliver the No. 3's to their former owner for choice, and so enable their old friends to get safely away. As for themselves, they proposed to return to camp and "take their medicine"--their dose and the portion that the aviation chief would otherwise be likely to get. But fate shuffled it another way. The workday was in the closing minutes. The remaining city thousands who were not in military service were swelling the stream of homegoers in the busy streets.