They had been walking for ten minutes when Miss Erith spoke in an ordinary tone of voice: "Kay? Do you think we're likely to come out of this?"

"No," he said, not looking at her.

"But we'll get our information, you think?"

"Yes."

The girl fell a few paces behind him and looked up at the pigeons where they sat in their light lattice cage crowning his pack.

"Please do your bit, little birds," she murmured to herself.

And, with a smile at them and a nod of confidence, she stepped forward again and fell into the rhythm of his stride.

Very far away to the west they heard thunder stirring behind Mount Terrible.

It was late in the afternoon when he halted near the eastern edges of Thusis's Forest.

"Yellow-hair," he said very quietly, "I've led you into a trap, I'm afraid. Look back. We've been followed!"

She turned. Through the trees, against an inky sky veined with lightning, three men came out upon the further edge of the hog-back which they had traversed a few minutes before, and seated themselves there In the shelter of the crag. All three carried shotguns.

"Yellow-hair?"

"Yes, Kay."

"You understand what that means?"

"Yes."

"Slip off your pack."

She disengaged her supple shoulders from the load and he also slipped off his pack and leaned it against a tree.

"Now," he said, "you have two pistols and plenty of ammunition. I want you to hold that hog-back. Not a man must cross."

However, the three men betrayed no inclination to cross. They sat huddled in a row sheltered from the oncoming storm by a great ledge of rock. But they held their shotguns poised and ready for action.

The girl crept toward a big walnut tree and, lying flat on her stomach behind it, drew both pistols and looked around at McKay. She was smiling.

His heart was in his throat as he nodded approval. He turned and went rapidly eastward. Two minutes later he came running back, exchanged a signal of caution with Miss Erith, and looked intently at the three men under the ledge. It was now raining.

He drew from his breast a little book and on the thin glazed paper of one leaf he wrote, with water-proof ink, the place and date.

And began his message:

"United States Army Int. Dept No. 76 and No. 77 are trapped on the northwest edge of the wood of Les Errues which lies under the elbow of Mount Thusis. From this plateau we had hoped to overlook that section of the Hun frontier in which is taking place that occult operation known as 'The Great Secret,' and which we suspect is a gigantic engineering project begun fifty years ago for the purpose of piercing Swiss territory with an enormous tunnel under Mount Terrible, giving the Hun armies a road into France BEHIND the French battle-line and BEHIND Verdun.

"Unfortunately we are now trapped and our retreat is cut off. It is unlikely that we shall be able to verify our suspicions concerning the Great Secret. But we shall not be taken alive.

"We have, however, already discovered certain elements intimately connected with the Great Secret.

"No. 1. Papers taken from a dead enemy show that the region called Les Errues has been ceded to the Hun in a secret pact as the price that Switzerland pays for immunity from the Boche invasion.

"2nd. The Swiss people are ignorant of this.

"3rd. The Boche guards all approaches to Les Errues. Except by way of the Boche frontier there appears to be only one entrance to Les Errues. We have just discovered it. The path is as follows: From Delle over the Swiss wire to the Crucifix on Mount Terrible; from there east-by-north along the chestnut woods to the shoulder of Mount Thusis. From thence, north over hog-backs 1, 2, and 3 to the Forest of Thusis where we are now trapped.

"Northeast of the forest lies a level, treeless table-land half a mile in diameter called The Garden of Thusis. A BOCHE AIRPLANE LANDED THERE ABOUT THREE HOURS AGO.

"To reach the Forbidden Forest the aviators, leaving their machine in the Garden of Thusis, walked southwest into the woods where we now are. These woods end in a vast gulf to the north which separates them from the Forbidden Forest of Les Errues.

"BUT A CABLE CROSSES!

"That is the way they went; a tiny car holding two is swung under this cable and the pa.s.sengers pull themselves to and fro across the enormous chasm.

"At the west end of this cable is a hut; in the hut is the machinery--a drum which can be manipulated so that the cable can be loosened and permitted to sag.

"The reason for dropping the cable is a.n.a.logous to the reason for using drawbridges over navigable streams; there is only one landing-place for airplanes in this entire region and that is the level, gra.s.sy plateau northeast of Thusis Woods. It is so entirely ringed with snow-peaks that there is only one way to approach it for a landing, and that is through the canyon edging Thusis Woods. Now the wire cable blocks this canyon. An approaching airplane therefore hangs aloft and signals to the cable-guards, who lower the cable until it sags sufficiently to free the aerial pa.s.sage-way between the cliffs. Then the aviator planes down, sweeps through the canyon, and alights on the plateau called Thusis's Garden. But now he must return; the cable must be lifted and stretched taut; and he must embark across the gulf in the little car which runs on grooved wheels to Les Errues.

"This is all we are likely to learn. Our retreat is cut off. Two cable-guards are in front of us; in front of them the chasm; and across the chasm lies Les Errues whither the aviator has gone and where, I do not doubt, are plenty more of his kind.

"This, and two carbons, I shall endeavour to send by pigeon. In extremity we shall destroy all our papers and identification cards and get what Huns we can, RESERVING FOR OUR OWN USES one cartridge apiece.

"(Signed) Nos. 76 AND 77."

It was raining furiously, but the heavy foliage of chestnut and walnut had kept his paper dry. Now in the storm-gloom of the woods lit up by the infernal glare of lightning he detached the long scroll of thin paper covered by microscopical writing and, taking off the rubber bands which confined one of the homing pigeons, attached the paper cylinder securely.

Then he crawled over with his bird and, lying flat alongside of Miss Erith, told her what he had discovered and what he had done about it. The roar of the rain almost obliterated his voice and he had to place his lips close to her ear.

For a long while they lay there waiting for the rain to slacken before he launched the bird. The men across the hog-back never stirred. n.o.body approached from the rear. At last, behind Mount Terrible, the tall edges of the rain veil came sweeping out in ragged majesty. Vapours were ascending in its wake; a distant peak grew visible, and suddenly brightened, struck at the summit by a shaft of sunshine.

"Now!" breathed McKay. The homing pigeon, released, walked nervously out over the wet leaves on the forest floor, and, at a slight motion from the girl, rose into flight. Then, as it appeared above the trees, there came the cracking report of a shotgun, and they saw the bird collapse in mid-air and sheer downward across the hog-back. But it did not land there; the marksman had not calculated on those erratic gales from the chasm; and the dead pigeon went whirling down into the viewless gulf amid flying vapours mounting from unseen depths.

Miss Erith and McKay lay very still. The Hunnish marksman across the hog-back remained erect for a few moments like a man at the traps awaiting another bird. After awhile he coolly seated himself again under the dripping ledge.

"The swine!" said McKay calmly. He added: "Don't let them cross."

And he rose and walked swiftly back toward the northern edge of the forest.

From behind a tree he could see two Hun cable-guards, made alert by the shot, standing outside their hut where the cable-machinery was housed.

Evidently the echoes of that shot, racketing and rebounding from rock and ravine, had misled them, for they had their backs turned and were gazing eastward, rifles pointed.

Without time for thought or hesitation, McKay ran out toward them across the deep, wet moss. One of them heard him too late and McKay's impact hurled him into the gulf. Then McKay turned and sprang on the other, and for a minute it was a fight of tigers there on the cable platform until the battered visage of the Boche split with a scream and a crashing blow from McKay's pistol-b.u.t.t drove him over the platform's splintered edge.

And now, panting, b.l.o.o.d.y, dishevelled, he strained his ears, listening for a shot from the hog-back. The woods were very silent in their new bath of sunshine. A little Alpine bird was singing; no other sound broke the silence save the mellow, dripping noise from a million rain-drenched leaves.

McKay cast a rapid, uneasy glance across the chasm. Then he went into the cable hut.

There were six rifles there in a rack, six wooden bunks, and clothing on pegs--not military uniforms but the garments of Swiss mountaineers.