"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.