Fair went on ahead, still keeping to the water, though both horses were pretty well winded with the hard going it afforded, and at last drew up to let Selwood come alongside. He sat still for a moment. “Listen a bit,” he said, “do you hear anything different from the sounds of water and the murmuring of the big cut?” The sheriff listened sharply. “Yes,” he said presently, “I do. Sounds like wind.” “Exactly. Yet there isn’t any wind, more than the draft which always draws down the cañon. Now look closely at the wall. Watch that clump of willows yonder.” He pointed ahead and to the left where a dense green growth stood alone against the rock face. Selwood looked and for a moment his face did not change. Then, suddenly, his mouth fell open, his eyes grew wide with astonishment. “Great Scott!” he said, “_they’re blowing out from the wall_! There’s wind behind them!” Fair moved forward and dismounted, leaving Diamond in the stream. The sheriff followed. They stepped lightly across the strip of sand which lay between the water and the willows and Fair turned to the right, circling the clump. “Here,” he said, “that red steer and the man who drove it went into the wall. I found their tracks that day. They’ve been obliterated by the shifting sand since then.” He pushed aside a feathery branch and the sheriff at his shoulder craned an incredulous head to look into what seemed the mouth of a cave. “No—it’s not a cave,” said Fair at his surmise, “it’s a prehistoric underground passage. It leads straight into the heart of Mystery Ridge from this end, and it has an opening somewhere, attested to by this current of wind. This mouth is just wide enough to admit one steer at a time, one horse and rider—but—what more do you want?” “Great Scott!” cried Selwood again, “of all the impossible things! And not a soul on Nameless knows about it!” “Wrong!” said Fair, “Kate Cathrew and her riders know. That open plain yonder—it leads out to a town, doesn’t it? On the railroad?” “Marston—yes. A long way across.” “Water?” queried Fair. “Yes—at intervals. Springs. Do for driving—yes—not for range—too far apart.” “Exactly,” said Fair. “Now, sheriff, find the other end of this subterranean passage and I believe you’ll have solved the mystery of the disappearing steers.” Price Selwood held out his hand. It was trembling. “I can’t tell you what I owe you for this information, Mr. ——?” “Smith—yes,” said Fair smiling. “Smith. It means more than I can say—to me.” “It means as much—or more—to me,” returned the other, “I’ve given two years of my life to a still-hunt for Kate Cathrew. I’d give two more to see her brought to justice.” “And we’ll get her!” said the sheriff grimly though with a lilt of joy in his voice. “Oh, my Lord, just won’t we get her! We’ll follow this hole straight to its——”