They had got some little distance away from the wires when Frank suddenly came to a dead stop. His comrades halted instantly. "What is it?" whispered Wilson, who was nearest to him. "That blur ahead of us," returned Frank. "It looks a little more solid than the rest of the darkness." He pointed ahead and a little to the right. "I don't see anything," remarked Tom. "Neither do I," affirmed Billy. "I think I see a little blacker patch than usual," declared Bart. "And it seems to be moving." The corporal put his ear to the ground. "I think Sheldon is right," he said, after a moment of intense listening. "At any rate we'll take no chances. Slip into some of these shell holes and lie low. If it should be an enemy patrol and there are too many to tackle we'll let them go by. But if there aren't more than double our number we'll take a crack at them. Keep your weapons ready and let fly when I give the word." The ground was so pitted with craters from the heavy artillery duel that had been raging all the day before that they had no difficulty in finding shelter. Their prisoner, who judged by the preparations that some of his own comrades were approaching, was inclined to balk a little and delay matters, but a vigorous push of Bart's boot hastened his movements and he was tumbled in unceremoniously. And they blessed the precaution that had still left the gag in his mouth when they had unfastened his hands. More and more the blur ahead of them detached itself from the surrounding darkness, until even skeptical Tom and Billy knew that what they saw was a body of men bearing down steadily in their direction. Of course there was a chance that it was an American patrol out on an errand similar to their own, but it was unlikely, if that were so, that they would be going in the direction of the enemy's lines when the night was so far spent. Nearer and nearer came the party until not more than thirty feet lay between them and the American boys who knelt in the shell holes, with faces stern and set and fingers on the triggers of their rifles awaiting the word of command. But for some unknown reason the blur became motionless and remained so for several minutes. Then it receded, as though the party had changed its plan. "What do you suppose is the matter with them?" whispered Tom. "Do you think they've tumbled to our being here?" "How could they?" returned Frank. "They'd have to have the eyes of cats to see us in these holes." "I hope the corp will let us go after them," murmured Billy. "I'm all tuned up for a scrap."