Nack-yal followed suit.  The Indian, with a hand clutching his mustang’s mane, rode up a steep, sandy slope on the other side that Shefford would not have believed any horse could climb.  The burros plodded up and over the rim, with Withers calling to them.  Joe Lake swung his rope and cracked the flanks of the gray mare and the red mule; and the way the two kicked was a revelation and a warning to Shefford.  When his turn came to climb the trail he got off and walked, an action that Nack-yal appeared fully to appreciate.

From the head of this wash the trail wound away up the widening canyon, through greasewood flats and over greasy levels and across sandy stretches.  The looming walls made the valley look narrow, yet it must have been half a mile wide.  The slopes under the cliffs were dotted with huge stones and cedar-trees.  There were deep indentations in the walls, running back to form box canyon, choked with green of cedar and spruce and pinyon.  These notches haunted Shefford, and he was ever on the lookout for more of them.

Withers came back to ride just in advance and began to talk.

“Reckon this Sagi canyon is your Deception Pass,” he said.  “It’s sure a queer hole.  I’ve been lost more than once, hunting mustangs in here.  I’ve an idea Nas Ta Bega knows all this country.  He just pointed out a cliff-dwelling to me.  See it? . . .  There ’way up in that cave of the wall.”

Shefford saw a steep, rough slope leading up to a bulge of the cliff, and finally he made out strange little houses with dark, eyelike windows.  He wanted to climb up there.  Withers called his attention to more caves with what he believed were the ruins of cliff-dwellings.  And as they rode along the trader showed him remarkable formations of rock where the elements were slowly hollowing out a bridge.  They came presently to a region of intersecting canyon, and here the breaking of the trail up and down the deep washes took Withers back to his task with the burros and gave Shefford more concern than he liked with Nack-yal.  The mustang grew unruly and was continually turning to the left.  Sometimes he tried to climb the steep slope.  He had to be pulled hard away from the opening canyon on the left.  It seemed strange to Shefford that the mustang never swerved to the right.  This habit of Nack-yal’s and the increasing caution needed on the trail took all of Shefford’s attention.  When he dismounted, however, he had a chance to look around, and more and more he was amazed at the increasing proportions and wildness of the Sagi.

He came at length to a place where a fallen tree blocked the trail.  All of the rest of the pack-train had jumped the log.  But Nack-yal balked.  Shefford dismounted, pulled the bridle over the mustang’s head, and tried to lead him.  Nack-yal, however, refused to budge.  Whereupon Shefford got a stick and, remounting, he gave the balky mustang a cut across the flank.  Then something violent happened.