d through her troubled mind.

They sat upon the bank, and waited. The sentinel continued to march up
and down just the other side of the fire, occasionally throwing a
remark at the major, but usually with his face turned toward the house,
which was distant about five furlongs.

Suddenly Ruth observed that Major Marchand had in his palm a little
round mirror. He seemed to be manipulating it to catch the firelight.
Ruth saw in a moment what he was about.

The sentinel stopped in his beat with a smothered exclamation. His
back was to them and he was staring up at the open window of the house.

There came a flash of light from the window--another! Like lightning
the sentinel raised his rifle and fired pointblank into the opening on
the second floor.

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.

CHAPTER XXI

A NIGHT TO BE REMEMBERED

"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