Will felt little shivers as they were about to leave the final row of trees. He could not help it, knowing that they were going to give up shelter for those open spaces which, dusky though they were, were yet revealing.

"It's likely, in any event, that we'll be followed, isn't it?" he said. "If the Sioux search the valley, and they will, they're sure to find our traces. Then they'll come over the rim of the hills on our tracks."

"Well reasoned, Will," said the hunter. "You'll learn to be a great scout and trailer, if you live long enough. That's just what they'll do, and they'll hang on to our trail with a patience that a white man seldom shows, because time means little to the Indian. As I said before, when we're far out on the plains we must make an abrupt turn toward the north, and lose ourselves among the ranges. For a long time to come the mountains will be our best friends. I love mountains anyway, Will. They mean shelter in a wild country. They mean trees, for which the eyes often ache. They mean grass on the slopes, and cool running water. The great plains are fine, and they lift you up, but you can have too much of 'em."

They rode now into the open country and in its dusky moonlight Will could not at first restrain the feeling that in reality it was as bright as day. A few hundred yards and both gazed back at the circle of hills enclosing the valley, hills and forest alike looking like a great black blur upon the face of the earth. But from the depths of that circling island came a long, piercing note, instinct with anger and menace.

"Now that was plain talk," said Boyd. "It said that they had found our trail, that they knew we were white, that they wanted our scalps, and that they meant to follow us until they got 'em."

"Which being the case," said Will defiantly, "we have to say to them in reply, though our syllables are unuttered, that we're not afraid, that they may follow, but they will not take us, that our scalps are the only scalps we have and we like 'em, that we mean to keep 'em squarely on top of our heads, where they belong, and, numerous and powerful though the Sioux nation may be, and brave and skillful though its warriors are, they won't be able to keep us from finding our mine."

"That's the talk, Will, my boy. It sounds like Red Cloud, the great Ogalala, Mahpeyalute himself. Fling 'em your glove, as the knights did in the old time, but while you're flinging it we'll have to do something besides talking. We must act. Trailers like the Sioux can follow us even in the night over the plains, and the more ground we gain in the beginning the better."

He urged his horses into a long, easy gallop and Will promptly followed at the same gait. The night darkened somewhat, at which they rejoiced, and then lightened again, at which they were sad, but they continued the long, swinging pace, which the horses could maintain for hours.

"Try your glasses again, Will," said the hunter. "They will cut through the dark a long way, and maybe they can tell if the Sioux are now in the plain."

Young Clarke slowed his pace, and bending in the saddle took a long look.