On a sudden he heard above the soft roar of the waterfall an unusual sound that he could not define. He dropped flat behind a stone and listened. From the direction he had come swelled something that resembled a strange muffled pounding and splashing and ringing. Despite his nerve the chill sweat began to dampen his forehead. What might not be possible in this stonewalled maze of mystery? The unnatural sound passed beyond him as he lay gripping his rifle and fighting for coolness. Then from the open came the sound, now distinct and different. Venters recognized a hobble-bell of a horse, and the cracking of iron on submerged stones, and the hollow splash of hoofs in water.

Relief surged over him. His mind caught again at realities, and curiosity prompted him to peep from behind the rock.

In the middle of the stream waded a long string of packed burros driven by three superbly mounted men. Had Venters met these dark-clothed, dark-visaged, heavily armed men anywhere in Utah, let alone in this robbers' retreat, he would have recognized them as rustlers. The discerning eye of a rider saw the signs of a long, arduous trip. These men were packing in supplies from one of the northern villages. They were tired, and their horses were almost played out, and the burros plodded on, after the manner of their kind when exhausted, faithful and patient, but as if every weary, splashing, slipping step would be their last.

All this Venters noted in one glance. After that he watched with a thrilling eagerness. Straight at the waterfall the rustlers drove the burros, and straight through the middle, where the water spread into a fleecy, thin film like dissolving smoke.

Following closely, the rustlers rode into this white mist, showing in bold black relief for an instant, and then they vanished.

Venters drew a full breath that rushed out in brief and sudden utterance.

"Good Heaven! Of all the holes for a rustler!...There's a cavern under that waterfall, and a passageway leading out to a canyon beyond. Oldring hides in there. He needs only to guard a trail leading down from the sage-flat above. Little danger of this outlet to the pass being discovered. I stumbled on it by luck, after I had given up. And now I know the truth of what puzzled me most--why that cattle trail was wet!"

He wheeled and ran down the slope, and out to the level of the sage-brush. Returning, he had no time to spare, only now and then, between dashes, a moment when he stopped to cast sharp eyes ahead. The abundant grass left no trace of his trail. Short work he made of the distance to the circle of canyons. He doubted that he would ever see it again; he knew he never wanted to; yet he looked at the red corners and towers with the eyes of a rider picturing landmarks never to be forgotten.