"Something makes me feel queer too," said Fred.
Just then a shrill, weird inhuman shriek came from somewhere in the direction of the mountains: "Kreee-kreee-ee," almost blood-curdling in its penetrating sharpness, cutting through the air like a keen knife blade, and sending unpleasant shivers down the backs of all who heard.
Again and again it came, threatening, foreboding, like some evil spirit about to swoop upon its prey.
They listened, spellbound, thrilled in every nerve. It was not fear that seemed to clutch at their hearts and make them pound, or that struck them silent, it was an awing sense of something supernatural, something not quite real. It was as though they had suddenly caught a glimpse of a demon of the underworld.
The dread cry continued for some minutes, then gradually grew fainter, until it seemed smothered by the intervening hills.
Before any of the party gathered courage to speak, a tall figure, like a fleeting shadow, glided across the path in front of them, and rapidly disappeared into the darkness. He seemed bent on an errand and was going toward the northeast mountain ranges.
"It's the Indian," whispered Carl, as the form hurried into the darkness.
"What do you suppose that noise was?" queried Jerry in a low tone.
"Was it a hawk?" asked Fly cautiously, crowding nearer to Carl.
"I've heard hawks cry and eagles scream, but never like that," returned the Indian, his voice growing louder.
"What was it then?" asked Fly in a natural voice, gathering courage as the conversation progressed.
"I never heard one, of course," replied Carl slowly, "but I think that was the Thunder Bird."
"That's just what it was," exclaimed Dunk at once.
For some moments nobody spoke, then Carl said reflectively: "I suppose that Indian friend of ours heard it too, and is on the trail."
"You'd better look out or he'll get it before you do," commented the captain, who had heard of the mysterious stranger.
The following day the first box of material arrived from Kansas City, and was taken to Mr. Giles' machine shop, which, having formerly been the army stables, was a great deal larger than was needed for the machinist's work, and he was able to give Hawke and the boys a roomy space at the rear.