The hut screened his retreat to the wood’s edge.  From there he saw the aviator and his companion land on the platform; heard them shouting for the dead who never would answer from their Alpine deeps; saw the airman at last go away toward the plateau where he had left his machine; heard the clanking of machinery in the hut; saw the steel cable begin to sag into the canyon; and realised that the aviator was going back over France to the Boche trenches from whence he had arrived.

In a flash it came to McKay what he should try to do—­what he must do for his country, for the life of the young girl, his comrade, for his own life:  The watchers at the hog-back must never signal to that airman news of his presence in the Forbidden Forest!

The clanking of the cog-wheels made his steps inaudible to the man who was manipulating the machinery in the hut as he entered and shot him dead.  It was rather sickening, for the fellow pitched forward into the machinery and one arm became entangled there.

But McKay, white of cheek and lip and fighting off a deathly nausea, checked the machinery and kicked the carrion clear.  Then he set the drum and threw on the lever which reversed the cog-wheels.  Slowly the sagging cable began to tighten up once more.

He had been standing there for half an hour or more in an agony of suspense, listening for any shot from the forest behind him, straining eyes and ears for any sign of the airplane.

And suddenly he heard it coming—­a resonant rumour through the canyon, nearer, louder, swelling to a roar as the monoplane dashed into view and struck the cable with a terrific crash.

For a second, like a giant wasp suddenly entangled in a spider’s strand, it whirled around the cable with a deafening roar of propellers; then a sheet of fire enveloped it; both wings broke off and fell; other fragments dropped blazing; and then the thing itself let go and shot headlong into awful depths!

Above it the taut cable vibrated and sang weirdly in the silence of the chasm.

The girl was still lying flat under the walnut-tree when McKay came back.

Without speaking he knelt, levelled his pistol and fired across at the man beyond the hog-back.

Instantly her pistol flashed, too; one of the men fell and tried to get up in a blind sort of way, and his comrades caught him by the arms and dragged him back behind the ledge.

“All right!” shouted one of the men from his cover, “we’ve plently of time to deal with you Yankee swine!  Stay there and rot!”

“That was Skelton’s voice,” whispered Miss Erith with an involuntary shudder.

“They’ll never attempt that hog-back under our pistols now,” said McKay coolly.  “Come, Yellow-hair; we’re going forward.”

“How?” she asked, bewildered.