Therefore they ran at top speed. While they were not afraid and had not lost a whit of their nerve, they realized that discretion was the better part of valor, and their feet continued to hit the ground at breakneck speed, until again came to their ears the first faint sounds of the pursuing motorcycles. Gradually the sounds became more distinct, this telling the boys that their pursuers were gaining rapidly, although the rough condition of the ground made it impossible for the motorcycles to travel very fast. Finally, when he could run no more, Hal threw himself to the ground, and Chester immediately followed his example. For a few moments they lay there, panting, their tongues literally hanging out like worn out dogs. Then they sprang to their feet again, and making an abrupt turn to the right plunged into the underbrush right where it was the most dense. Here Hal espied a large tree, with low hanging branches. With Chester by his side he rushed for it. Hal stood aside while Chester grabbed the lowest branch and swung himself up, and then he followed suit. High up in the tree the lads climbed, the close set branches affording an excellent screen. Half a minute later six motorcycle riders hove into sight, hardly a hundred yards from where the boys were perched. Chester's fingers twitched on his revolver, but Hal, who had noticed the set expression on his friend's face, uttered a low warning. And the sound of Hal's voice was almost their undoing. For the Germans had come to a pause and Hal's words carried plainly in the silence to their ears. For a moment the Germans glanced about hurriedly, seeking out their prey. Then they sprang behind trees themselves, their rifles ready to fire. They had not yet discovered the boys' hiding place, and were fearful of a shot from ambush. Then one, raising his eyes, saw Hal, and quickly raised his rifle. But Hal's eye was keen also, and before the German could press the trigger Hal's revolver spoke and the German tumbled to the ground. Chester fired at the same moment as did Hal, and a second German clapped his hand to his head and reeled. But before the other pursuers could raise their rifles, there came from ahead a sound that brought a loud "Hurrah" from Hal and Chester, and a moment later, on the dead run, came a small body of British infantry. Quickly the Germans leaped onto their motorcycles and turned to run. But now the advancing British were in full view, and a voice of command rang out: "Fire!" A volley rang out. Not in all the world were there better marksmen than those British troopers. Four Germans reeled in their saddles and tumbled to the ground. Hal and Chester descended from their place of refuge. CHAPTER XVIII. ON A NEW MISSION. The two lads hurried up to the officer in command of the English troops. "You arrived just in time," cried Hal, grasping the hand the officer extended.