The Hun hung low above them in mid-air, slowly wheeling over the gulf. Perhaps it was his shadow or the roar of his engines that routed out the lammergeier, for the unclean bird took the air on enormous pinions, beating his way upward till he towered yelping above the Boche, and their combined clamour came distinctly to the two watchers below.
Suddenly the Boche fired at the other winged thing; the enraged and bewildered bird sheered away in flight and the Hun followed.
"That's why he shot," said McKay. "He's got a pilot, now."
Eagle and plane swept by almost level with the forest where they stood staining with their shadows the white shoulder of Thusis.
Down into the gorge the great geier twisted; after him sped the airplane, banking steeply in full chase. Both disappeared where the flawless elbow of Thusis turns. Then, all alone, up out of the gulf soared the plane.
"The Hun has discovered a landing-place in Les Errues," said McKay. "Watch him."
"There's another Hun somewhere along the shoulder of Thusis," said McKay. "They're exchanging signals. See how the plane circles like a patient hawk. He's waiting for something. What's he waiting for, I wonder?"
For ten minutes the airplane circled leisurely over Thusis. Then whatever the aviator was waiting for evidently happened, for he shut off his engine; came down in graceful spirals; straightened out; glided through the canyon and reappeared no more to the watchers in the forest of Thusis.
"Now," remarked McKay coolly, "we know where we ought to go. Are you ready, Yellow-hair?"
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.