With face upraised to the breath of air which stirred across the bare black lava hills, Rathburn leaned forward in the saddle eagerly, while his dun-colored horse stood patiently, seemingly in accord with his master's mood. A merciless sun beat down from a hot, cloudless sky. Below, stretching in endless miles was the desert--a sinister, forbidding land of desolate distances, marked only by slender yucca palms, mesquite, dusty greasewood, an occasional clump of green palo verde, the slim fingers of the ocatilla, the high "forks" of the giant sahuara, and clumps of la cholla cactus, looking like apple orchards in full bloom. Yet the man's gaze fell for a moment lovingly on each species of cactus and desert vegetation; his look was that which dwells in the homesick eyes of a traveler when he sees his native land from the deck of an inbound ship. "Hoss, we're home!" he said aloud, while the animal pricked up its ears. Then he looked off to the left, where the blue outlines of a low range of mountains wavered in the heat like a mirage. "Imagination Range," he said moodily. He tickled the dun with his spurs and trotted along the crest of the lava ridge. At its eastern terminus he swung down into the desert and struck straight east in the direction of Imagination Range. The desert's surface between the lava ridge and the higher hills of the range to eastward was cut by dry washes and arroyos and miniature ridges studded with giant cactus. On the top of one of these high rises the horseman suddenly reined in his mount and stared into the south. "There's trouble--an' spelled with a capital T!" he ejaculated. The gaze in his keen gray eyes centered upon a number of riders speeding their horses over the tumbled section of desert below him to his right. He made out two divisions of horsemen. One group was some distance ahead of the other. Even as he stared down at them, its group separated, and some rode for Imagination Range, while others hastened toward the lava hills, or due north in his direction. The second group halted for a brief spell, evidently for a conference, and then its members also divided and started in swift pursuit of the men ahead. The watcher on the top of the rise frowned. "Out of here, hoss," he said sharply. "This ain't our day for visitors." He pushed on eastward, increasing its pace, but losing time in skirting the frequent bits of high ground. As he rode down into a deep arroyo, a horseman came galloping into its lower end and raced almost upon him before seeing him. His hand darted like lightning to his gun, and the weapon snapped into aim at his hip. The horseman came to a rearing halt, reins dangling, his hands held high, his eyes bulging from their sockets. "Rathburn!" he exclaimed. "The same," said the man with the gun. "What's all the disturbance down there?" "Bob Long is chasing us," the other answered with a nervous grin.