It had been a beautiful ravine where Recklow now stood--was still as pretty and picturesque as a dry water-course can be with the bowlders bleaching in the sun and green things beginning to grow in what had been the bed of a rushing stream. For, just above this ravine, the water ended: the Staubbach poured its full, icy volume directly downward into the bowels of the earth with a hollow, thundering sound; the bed of the stream was bone-dry beyond. And now the blue-devils were unreeling wire and plumbing this chasm into which the Staubbach thundered. On the end of the wire was an electric bulb, lighted. Recklow watched the wire unreeling, foot after foot, rod after rod, plumbing the dark burrow of the Boche deep down under the earth.

And, when they were ready, guided by the wire, they lowered the curious hose-pipe, down, down, ever down, attaching reel after reel to the lengthening tube until Recklow checked them and turned to watch the men who stood feeding the wire into the roaring chasm.

Suddenly, as he watched, the flowing wire stopped, swayed violently sideways, then was jerked out of the men's hands.

"The Boche bites!" they shouted. Their officer, reading the measured wire, turned to Recklow and gave him the depth; the hose-pipe ran out sixty yards; then Recklow checked it and put on his gasmask as the whistle signal rang out along the mountain.

Now, everywhere, masked figures swarmed over the place; cylinders were laid, hose attached, other batteries of cylinders were ranged in line and connections laid ready for instant adjustment.

Recklow raised his right arm, then struck it downward violently. The gas from the first cylinder went whistling into the hose.

At the same time an unmasked figure on the cliff above began talking by American radiophone with three planes half a mile in the air above him. He spoke naturally, easily, into a transmitter to which no wires were attached.

He was still talking when Recklow arrived at his side from the ravine below, tore off his gas-mask, and put on a peculiar helmet.

Then, taking the transmitter into his right hand: "Do you get them?"

he demanded of his companion, an American lieutenant.

"No trouble, sir. No need to raise one's voice. They hear quite perfectly, and one hears them, sir."

Then Recklow spoke to the three airplanes circling like hawks in the sky overhead; and one by one the observers in each machine replied in English, their voices easily audible.

"I want Zell watched from the air," said Recklow. "The Boche have an underground tunnel beginning near Zell, continuing under Mount Terrible to the French frontier.

"I want the Zell end of the tunnel kept under observation.

"Send our planes in from Belfort, Toul, Nancy, and Verdun.

"And keep me informed whether railroad trains, camions, or cavalry come out. And whether indeed any living thing emerges from the end of the tunnel near Zell.

"Because we are ga.s.sing the tunnel from this ravine. And I think we've got the dirty vermin wholesale!"

At sundown a plane appeared overhead and talked to Recklow:

"One railroad train came out. But it was manned by dead men, I think, because it crashed into the rear masonry of the station and was smashed."

"Nothing else, living or dead, came out?"

"Nothing, sir. There is wild excitement at Zell. Troops at the tunnel's mouth wear gas-masks. We bombed them and raked them. The Boche planes took the air but two crashed and the rest turned east."

"You saw no living creature escape from the Zell end of the tunnel?"

"Not a soul, sir."

Recklow turned to the group of officers around him:

"I guess they're done for," he said. "That fumigation cleaned out the vermin. But keep the tunnel pumped full of gas.... Au revoir, messieurs!"

On his way back across Mount Terrible he encountered a relay of Alpinists bringing fresh gas. tanks; and he laughed and saluted their officers. "This poor old world needs a de-lousing," he said.

"Foch will attend to it up here on top of the world. See that you gentlemen, purge her interior!"

The nurse opened the door and looked into the garden. Then she closed the door, gently, and went back into the house.

For she had seen a slim girl with short yellow hair curling all over her head, and that head was resting on a young man's shoulder.

It seemed unnecessary, too, because there were two steamer chairs under the rose arbor, side by side, and pillows sufficient for each.

And why a slim young girl should prefer to pillow her curly, yellow head upon the shoulder of a rather gaunt young man--the shoulder, presumably, being bony and uncomfortable--she alone could explain perhaps.

The young man did not appear to be inconvenienced. He caressed her hair while he spoke:

"From here to Belfort," he was saying in his musing, agreeable voice, "and from Belfort to Paris; and from Paris to London, and from London to Strathlone Head, and from Strathlone Head to Glenark Cliffs, and from Glenark Cliffs to Isla Water, and from Isla Water--to our home! Our home, Yellow-hair," he repeated. "What do you think of that?"

"I think you have forgotten the parson's house on the way. You are immoral, Kay."

"Can't a Yank sky-pilot in Paris--"

"Darling, I must have some clothing!"

"Can't you get things in Paris?"

"Yes, if you'll wait and not become impatient for Isla. And I warn you, Kay, I simply won't marry you until I have some decent gowns and underwear."

"You don't care for me as much as I do for you," he murmured in lazy happiness.

"I care for you more. I've cared for you longer, too."

"How long, Yellow-hair?"

"Ever--ever since your head lay on my knees in my car a year ago last winter! You know it, too," she added. "You are a spoiled young man. I shall not tell you again how much I care for you!"

"Say 'love',' Yellow-hair," he coaxed.

"No!"

"Don't you?"

"Don't I what?"

"Love me?"

"Yes."

"Then won't you say it?"

She laughed contentedly. Then her warm head moved a little on his shoulder; he looked down; lightly their lips joined.

"Kay--my dear--dear Kay," she whispered.

"There's somebody opening the garden door," she said under her breath, and sat bolt upright.