Then, with a shout, he dashed across the intervening space and disappeared within the house. Major Marchand seized Ruth's hand and rose to his feet.
"Come!" the French officer whispered. "Now is our chance."
"Oh!" Ruth murmured, scarcely understanding.
"Haste! He will be back in a minute," the officer said.
He helped her over the dyke, and, stooping, they ran away from the abandoned house from which the puzzled American sentinel thought he had seen a spy flashing a light signal to the enemy lines.
"Fortunately, I had a little mirror," murmured Major Marchand, as he and the girl hurried on through the dusk. "With it, you see, I flashed a reflection of the firelight upon the broken panes of that upper window. Our brave young American will discover his mistake before his relief comes. We could not wait for that. Nor could we easily explain to his top-sergeant why we wished to go forward."
"Oh!" murmured Ruth again. "In your work, Monsieur, I see you have to take chances with both sides."
"It is true. Our own friends must not suspect too much about us. The best spy, Mademoiselle, plays a lone hand. Come! This way. We must dodge these other sentinels."
It was evident that he knew the vicinity well. Beyond the mesa they descended through a grove of big trees, whose tops had been shot off by the German guns.
They traveled through the lowland swiftly but cautiously. Ruth could not see the way, and clung to Major Marchand's hand. But she tried to make no sound.
Once he drew her aside into a jungle of brush and they crouched there, completely hidden, while a file of soldiers marched by, their file leader flashing an electric torch to show the way.
"The relief," whispered Major Marchand, when they had gone. "They may be swarming down this hill after us in a few minutes."
The two hurried on. The keen feeling of peril and adventure gripped Ruth Fielding's soul. It was not with fear that she trembled now.
At length they halted in a pitch-black place, which might have been almost anything but the sheepfold Major Marchand told Ruth it was. He produced an officer's trench whistle and blew a long and peculiar blast on it.
"Now, hush!" he whispered. "It is against usage to use these whistles for anything but the command to go over the top at 'zero.' Necessity, however, Mademoiselle, knows no law."