rest? Danny could never know. He knew only that he stood rigid with horror, entirely unable to move, while that rod swung upon him; he knew that the hand that held it released something that clicked, wherefore his life had been spared; and he knew that the savage face above wrinkled into something resembling a snarling, triumphant smile, as the rod was returned to its hiding place under the garment of shimmering blue, and the mysterious figure turned and strode savagely down the Avenue Stalin in the city of Stobolsk.

Danny O'Rourke was to carry that picture clearly in his mind—the figure that moved unhurriedly on, towering above the others, men and women, who scurried fearfully from his path. But he was to retain yet more vividly the recollection of a group of red-clad bodies that were severed at their waists as a slim tube swung—then a bursting cloud of oily smoke, and a pool of molten rock where they had been.

Something of this, perhaps, was clouding the eyes of Danny O'Rourke, Pilot of the A.F.F. a month and more later, as he sat at lookout duty in a gleaming white tower on a high peak of the Sierras. Not that the job of lookout was part of O'Rourke's duty, now that he was back in the U. S. A., but a cylinder of scarlet rested on a great rack at the base of the tower, and Danny had no wish to hear the roar of that cylinder's stern exhaust for a time.

Even the novelty of flying the newest rocket-ship in the service had worn off. Besides, he had patrolled his route, and he told himself that the "Infant" needed a rest.

The "Infant," better known on the records of the A. F. F. as Morgan, David E., Lookout, Station 39-G, was sleeping soundly on the elevating table where a map of the district was mounted under glass. His cherubic face was pink and white, more suggestive of the age of three than of twenty-three. And O'Rourke, glancing at him protectingly, hung up a paper to keep the sunlight from striking the young man's face.

The Infant had been Danny's special charge from the day he entered the service, and now, except for the Chief and some other officials, only Danny knew that the Infant was there to teach and not to learn. For behind those eyes that might have been taken from one of Rafael's cherubim lay a brain that Danny had learned to respect.

"Fifteen minutes more. I'm givin' you," he said inaudibly; "then I'll be on my way, and you'll do your own squintin' and peekin'." But the Infant's fifteen minutes were cut to that many seconds—

Danny had been looking toward the south before he had turned to gaze at the Infant: his eyes came back to the same point to take up their reconnaissance. But now, where clear sky had made a blue back-drop for rugged peaks, was a line of black. And the line, while Danny watched in disbelief, moved like a smoky serpent: its head stretched out and out while from behind it there came the ominous line of black.

All this happened in a matter of seconds, and the moving head ceased at last to move; the line no longer grew. But, where it had been at first a thin mark of black, it changed now to billowing gray.

It was fifty miles away at least; but it showed clear and sharp. And the first gray had hardly bloomed from its black beginning before the long arm of Danny O'Rourke had swept the sleeping Infant to the floor, while, with the other hand, he swung an instrument of telescopic sights upon distant smoke.

He set it in careful focus—took a reading for distance—another for direction—and while he was doing it he was vaguely conscious of one single sharp flash in the sky above that far-off cloud. In his range-finder it showed once, like a glittering star; then it vanished, but the trained eye of O'Rourke observed its passage like a ray of light overhead.

The pink-faced youngster on the floor was still protesting sleepily when O'Rourke slammed down a switch and heard a voice answer promptly from an instrument on the wall. Danny shouted out his bearings on the fire:

"Thirty-nine-G! O'Rourke speaking for Morgan. Reporting fire on a wide front—bearing Two-O-Seven to Two-Four-Nine! And for God's sake, Chief, get a line on this quick. The whole thing shot up in a second—fifty miles of fire!"

Another voice broke in excitedly. "Station Fourteen-Fourteen-Fourteen!" The voice was stammering in evident confusion. "The whole earth has exploded—it's on fire now! I—I—"

The Chief's voice broke in with a quiet, "Bearing, please! Report your bearing, Fourteen!"

And the stammering voice steadied to give a figure.

"Headquarters speaking," said the quiet voice. "Orders for O'Rourke. For the love of Pete, get on that fire, Danny. Every instrument in the office is chattering. Every patrol ship has spotted that blaze. You can't all be crazy. It's in Section Eight—never mind the exact bearings—you'll find it without any trouble I imagine. Now beat it! And let me know what kind of a fire this is that starts on a fifty-mile front! You're in charge till I come."

Ten seconds later, had the Infant been watching, which he had not—for his eyes were all on the distant smoke—he would have seen the beautiful curving sweep of a scarlet projectile, whose screaming propeller swept her off and up; he would then have seen it lie back flat as the great stern exhaust made a rocket of the ship to send it roaring into the heights.

And in the air-tight cabin of the newest fire-fighting machine of the A. F. F., Danny O'Rourke pulled his body out of the slumped position into which his quick acceleration had forced him; then set his ship on her course to where a distant smoke made puffballs of gray against a cloudless sky. And, like his Chief, he was wondering with a wonderment that bordered upon disbelief what manner of fire this was that shot like a fifty-mile serpent across mountains and valleys.

He was over it in less than ten minutes, flying high to clear the tiny dots slipping swiftly across his view-finder. They were other firecraft; he saw them darting in and down from all sides. For himself, he took the line of smoke at its western end where it had begun. Here it would be at its worst, perhaps, although no reports were in as yet.

The radio had been bringing in messages unceasingly as patrols and firecraft answered the call. Some nearer than himself were reporting themselves "on the fire"; he saw them grouped in the usual echelon formation up to windward of the blaze. They darted down and in as he looked, and Danny thrilled at the sight which had never yet failed to reach the core of his emotional Irish nature.

The smoke and fire swallowed them up; their red bodies and short black wings drove unswervingly into the holocaust of flame.

"Like a bunch o' bats out o' hell!" said Danny admiringly. "And 'tis hell they're goin' into!" Which fact there was none to dispute with Danny O'Rourke who knew, if any man did, the full truth of the remark.

He saw them as they struck the fire; saw the whirling blast of snow that drove under them as they went into the fight with the wildest enemy of man; and he knew that a smothering blanket of carbon dioxide was driving with hurricane force upon the flames.

On the instrument at his side flashed the "Ascend!" order of the squadron commander, and an instant later the flight reappeared a half mile away.

The commander must have sighted O'Rourke's ship. "Shall we repeat over same course?" the instrument spelled out, while Danny, circling above, watched the effects of the drive.

It had checked the flames, that first blast of the CO_2 squadron; he saw blackened, jagged trees where a roaring furnace had been. But the flames were building up again. "Repeat!" O'Rourke answered; then watched them drive in again.

From a wooded valley beyond a low range came a call for help. A lone ship in the red and black of the service had driven down into that valley that