And Wildfire was lame and in distress and Nagger was growing gaunt and showing strain; and Slone, haggard and black and worn, plodded miles and miles on foot to save his horse.

Slone felt that it would be futile to put the chase to a test of speed.  Nagger could never head that stallion.  Slone meant to go on and on, always pushing Wildfire, keeping him tired, wearied, and worrying him, till a section of the country was reached where he could drive Wildfire into some kind of a natural trap.  The pursuit seemed endless.  Wildfire kept to open country where he could not be surprised.

There came a morning when Slone climbed to a cedared plateau that rose for a whole day’s travel, and then split into a labyrinthine maze of canyons.  There were trees, grass, water.  It was a high country, cool and wild, like the uplands he had left.  For days he camped on Wildfire’s trail, always relentlessly driving him, always watching for the trap he hoped to find.  And the red stallion spent much of this time of flight in looking backward.  Whenever Slone came in sight of him he had his head over his shoulder, watching.  And on the soft ground of these canyons he had begun to recover from his lameness.  But this did not worry Slone.  Sooner or later Wildfire would go down into a high-walled wash, from which there would be no outlet; or he would wander into a box-canyon; or he would climb out on a mesa with no place to descend, unless he passed Slone; or he would get cornered on a soft, steep slope where his hoofs would sink deep and make him slow.  The nature of the desert had changed.  Slone had entered a wonderful region, the like of which he had not seen—­a high plateau crisscrossed in every direction by narrow canyons with red walls a thousand feet high.

And one of the strange turning canyons opened into a vast valley of monuments.

The plateau had weathered and washed away, leaving huge sections of stone walls, all standing isolated, different in size and shape, but all clean-cut, bold, with straight lines.  They stood up everywhere, monumental, towering, many-colored, lending a singular and beautiful aspect to the great green-and-gray valley, billowing away to the north, where dim, broken battlements mounted to the clouds.

The only living thing in Slone’s sight was Wildfire.  He shone red down on the green slope.

Slone’s heart swelled.  This was the setting for that grand horse—­a perfect wild range.  But also it seemed the last place where there might be any chance to trap the stallion.  Still that did not alter Slone’s purpose, though it lost to him the joy of former hopes.  He rode down the slope, out upon the billowing floor of the valley.  Wildfire looked back to see his pursuers, and then the solemn stillness broke to a wild, piercing whistle.

Day after day, camping where night found him, Slone followed the stallion, never losing sight of him till darkness had fallen.  The valley was immense and the monuments miles apart.  But they always seemed close together and near him.  The air magnified everything.  Slone lost track of time.  The strange, solemn, lonely days and the silent, lonely nights, and the endless pursuit, and the wild, weird valley—­these completed the work of years on Slone and he became satisfied, unthinking, almost savage.