Through an airplane’s thick windows of shatter-proof glass, so tough and resilient that a machine-gun bullet would only make a temporary dent, the midday sun flashed brightly as the big ship rolled. Along each side of the small room, high up under the curve of the cabin roof, windows were ranged. Others like them were in the floor. And, above, the same glass made a transparent dome from which an observer could see on all sides.

Outside was the thunderous roar of ten giant motors, but inside the cabin the fire-control room of a dreadnought of the air that blast of sound became more a reverberation and a trembling than actual noise.

Certainly the sound of motors and of slashing propellers, as the battle plane roared up into the sky, did not prevent free conversation among the three men in the room. Yet there was neither laughter nor idle talk.

At a built-in desk, before a battery of instruments, sat Farrell, the captain of the ship. Farther aft, in solidly anchored chairs, Colonel Culver and Smithy were seated. Occasionally the captain spoke into a transmitter, cutting in by phone on different stations about the ship.

“Check up on that right-wing gun, Sergeant number two of the top wing-battery. Recoil mechanism is reported stiff.... Tell Chicago, Lieutenant, we will want one thousand gallons in the air gas only no oil needed.... Gun room? Have the gun crews get some sleep. They’ll have to stand by later on....”

Colonel Culver spoke musingly. “Guerilla warfare, the hardest kind to meet.”

Smithy nodded absently. He rose and stared from one of the side windows that was just level with his eyes. He could see nothing but the broad expanse of wing, a sheet of smooth gray metal. Along its leading edge was a row of shimmering disks where great propellers whirled. From the top of the wing a two-inch Rickert recoilless thrust forth its snout; it rose in air till the whole weapon was visible, then settled again and buried itself inside the wing.

They were testing a gun. Smithy knew that inside that wing section were other guns, and men, and smoothly running motors. The whole ship was only a giant flying wing of which their own central section was merely a thickening.

He looked down through a bull’s-eye in the floor. The city they had just left was beneath them. Washington, the nation’s capital; the golden dome of the Capitol Building was slipping swiftly astern. Only then did he make a belated reply to Culver’s statement.

“Well,” he said shortly, “they’ll have to meet it their own way. We told them all we knew. And a lot of good that did not!”

“Five days!” said Culver. “It seems more like five years since the devils first came out. Nobody knows where they will hit next. But they’re working north and there’s no trouble in telling where they’ve been.”

Smithy’s voice was hot in reply, hot with the intense anger of a young, aggressive man when confronted by the ponderous motion of a big organization getting slowly under way.

“If only we’d gone down underground,” he exclaimed; “carried the fight to them! They live there there must be a whole world underground. We could have carried in power lines, lighting the place as we went along. We could have fought ’em with gas. We’d have paid for it, sure we would, but we’d have given them enough hell to think of down below so they wouldn’t raise so much of it up above.

“But no! We had to fight according to the textbooks. And those red devils don’t fight that way; they never learned the rules.”

“Guerilla warfare,” Colonel Culver repeated. “There are certain difficulties about fighting enemies you can’t see.”

“They’re clever,” Smithy admitted. “We taught them their lesson down there in the desert they’ve never been seen in daylight since. Out at night and their invisible heat-rays setting fire to a city a mile away, then mopping up with their green flame-throwers if anyone’s left. They pick our planes out of the sky even when they’re flying without lights. Darkness means nothing to them! It was murder to send troops in against them, troops wiped out to a man! Artillery that’s no good either when we don’t know how many of the devils there are, or where they are. There’s no profit in shelling the place when the brutes have gone back underground.”

Colonel Culver shot a warning glance from Smithy to the seated officer. “About a hundred square miles of the finest fruit country on earth laid waste,” he admitted gravely; then sought to turn Smithy from his rebellious mood:

“What’s underground, I wonder? Must be a world of caves. Or perhaps these mole-men can follow up a mere crack or a fault line and open it out with their flame-throwers to make a tunnel they can go through.”

The plane’s captain had caught Culver’s glance. “Speak your piece,” he said pleasantly. “Don’t stop on my account. There’s a lot to what Mr. Smith says but you don’t know all that’s going on.”

He had been half turned. Now he swung about in his little swivel chair, whose base was riveted solidly to the floor and whose safety belt ends dangled as he turned.

“My orders are to deliver you two gentlemen at San Francisco. But there’s a show scheduled for to-night down south of there two hundred planes, big and little, scouts, cruisers, battle planes. They’re going to swarm in over when the enemy makes his first crack. There’s a devil of a storm in the mountains along the route we would usually take. I’m afraid I’ll have to swing off south.” He was grinning openly as he turned back to his desk.

Colonel Culver smiled back. “Attaboy!” he said.

But Smithy’s forehead was still wrinkled in scowling lines as he walked forward to an adjoining room. “Underground,” he was thinking. “We’ve got to carry the fight to them; got to lick ’em so they’ll stay licked. But Rawson good old Dean we’re too late to help him. And the lives of all the devils left in hell can’t pay for that.”

Smithy had been dozing. The shrill whistle of a high-pitched siren brought him fully awake in an instant. Culver, too, sprang alertly to his feet. Both men knew the signal was the call to quarters.

They had spread blankets on the floor of the fire-control room. Culver immediately folded his into a compact bundle, and Smithy followed suit, as he said: “That’s right; we don’t want any feather beds flying around here in case of a mix-up.”

Even Culver’s simple act of stowing the blankets back in their little compartment thrilled him with what it portended. His nerves were suddenly aquiver with anticipation. A real fight! A determined effort! No telling what these big dreadnoughts could do. Two hundred, big and little, Captain Farrell had said. If they could catch the enemy out in the open, show him up in a blaze of enormous flares....

Captain Farrell was calling them. A section of the floor had been raised up mysteriously to form a platform beneath the shallow dome of the conning tower. Farrell was there, headphones clamped to his ears, one hand on the little switchboard at the base of the glass dome that kept him in touch with every station on the ship. Beside him was the fire-control officer similarly equipped, though his headphone was connected only with the gun crews.

“The enemy’s out!” said Captain Farrell. “And not just where they were expected they’re raising fourteen kinds of hell. The ships have been ordered in. I’m hooked up with the radio room now. They’re less than a hundred miles ahead. Of course we won’t mix in on it, but I thought it best to have my men standing by.”

He pressed a little lever on his switchboard and spoke into the mouthpiece of his head-set. “Pilot room? Our two passengers, Colonel Culver and Mr. Smith, are coming forward. Let them see whatever they can of the show.”

He gave the two a quick smile and a nod and waved them forward with the binoculars in his free hand. “It will be ‘lights out’ after you get there. We’ll be flying dark except for wing and tail lights up on top. The enemy’s movements are uncertain; perhaps he can see us anyway, but we won’t advertise ourselves to him.”

The ship’s bow was a blunt, rounded nose of glass, cut by cross bars of aluminum alloy. That deeper central portion of the big flying wing was carried ten feet forward; it was but one of many details that Smithy had looked at with interest when he had seen the ship waiting for them on the field.

The pilot room was dark when they entered. Only the glow from the instrument panel showed the two men who were seated behind the wheel controls. One of them turned and nodded a welcome.

“Can’t offer you gentlemen seats,” he said, “but if you’ll stand right here behind us you can see the whole works.” He did not wait for a reply, but turned back toward the black night ahead.

Smithy glanced past him at the lighted instruments and found the altimeter. Twelve thousand yes, there was nasty country hereabouts. Then he, too, stared out into the dark at the sky sprinkled with stars, at the vague blur of an unlighted world far below, and off at either side and behind them the quivering lines of cold light where starlight was reflected dimly from the spinning propellers.

Other wing lights winked out as he watched, and he knew that from that moment on, they were invisible from below invisible to human eyes at least that they were sweeping on through the darkness like some gargantuan night bird pursuing its prey.

“Flares ahead, sir,” one of the pilots had spoken into the mouthpiece of his telephone, spoken lightly, reporting back to Captain Farrell. The words whipped Smithy’s head about, and he, too, saw on a distant horizon, the beginning of a white glare.

They were fighting there two hundred planes roaring downward, one formation following another. In his mind he was seeing it so plainly.

The white blaze of light dead ahead grew broader. It had not been as far distant as he had first thought, and the scene that he had pictured came swiftly to reality.

Their own ship was still at the twelve-thousand-foot level. Ahead, and five thousand feet below, tiny lights, red and white and green, lights whose swift motion made their hundreds seem like thousands instead, were weaving intricate patterns in the night. The flying lights of the fighting planes were on for the planes’ own protection; and, too, no further concealment was possible in the glare that shone upward from below.

Settling downward were balls of blinding fire, flares dropped by the squadron of scout planes that had torn through in advance. They lighted brilliantly a valley which, a few hours before, had been one of many like it square fields, dark green with the foliage of fruit trees, straight lines of crossing roads, houses, and off in the distance a little city.

And now the valley was an inferno of spouting flame. That city was a vast, roaring furnace under smoke clouds of mingled blood-red and black. The valley floor was a place of desolation, of drifting smoke and of flashing shell-bursts as the fleet swept in above.

The myriad lights of the planes had drawn into a circle, a great whirlpool of lines that revolved above a mile-wide section of that valley.

Beside Smithy a wheel control was moving. He clung to the pilot’s seat as their own plane banked and nosed downward. And now he shouted aloud to Culver:

“The mole-men! There they are! Thousands of them!”

He was pointing between the two pilots as their own plane swept down. He could see them plainly now, clotted masses of dark figures surging frenziedly to and fro. For an instant he saw them then that part of the world where they had been was a seething inferno of bursting bombs and shells.

Beside him Colonel Culver spoke quietly: “Caught them cold! That’s handing it to them.”

Their own plane had leveled off. With motors throttled they were drifting slowly past, only a thousand feet higher than the circling planes just off at one side. Culver’s quiet tones rose to a hoarse shout: “The ships! My God, they’re falling!”

His wild cry ended in a gasp. Beside him Smithy, in breathless horror, like Culver, was staring at that whirlpool of tiny lights that had gone suddenly from smooth circular motion into frenzied confusion, or vanished in the yellow glare of exploding gas tanks. The light of their own white flares picked them out in ghastly clarity as they fell.

Straight, vertical lines of yellow were burning planes. Again they made horrible zigzag darts and flashed down into view torn and helpless, while others, tens and scores of others with crumpled wings, joined the mad dance of death.

Smithy knew that he could never tear his eyes away from the sight. Yet within him something was clamoring for his attention. “They didn’t do it from below!” that something was shouting. “Not down in that hell. There are more of them somewhere.” Then somehow, he forced his eyes to stare ahead and outside of that circle of fearful fascination and he knew that for an instant he was seeing a single stab of green flame.

One single light on the darkness of a little knoll that stood close beside this place of white flame and destruction. One light and in the valley there had flashed a million brighter. It had shone but an instant, but, to Smithy, watching, it was the same he had seen when their own camp was attacked. And now it was Smithy who was abruptly stone cold.

One hand closed upon a pilot’s shoulder with a grip of steel; his other pointed. “Down there they’re hiding back of that hill, picking off our ships from the side.” And then, like a guiding beacon, a point of green showed once more.

The plane banked sharply while one of the pilots spoke crisp, clearly enunciated words into his phone. He listened; then: “Right!” he snapped. “Power dive for bow-gun firing. Level off for bombing from five hundred feet.”

Off into the night they were headed. Then a left bank and turn brought the place of blazing flares and falling planes swinging smoothly into view; they were flying toward it.

Against the white glare in the valley of death was a hill, roundly outlined. Then the ship’s nose sank heavily down; and, from each broad wing, in straight, forward-stabbing lines, was the steady lightning of the Rickert batteries in action.

The pilot’s room was a place of unbearable sound. The crash of gunfire, it seemed, must crush the glass wall like an eggshell by the sheer impact of its own thunder. In that pandemonium Smithy never knew when they flattened out. He knew only that the hill ahead twinkled brilliantly, and that each flashing light was an exploding shell. He knew when the hill passed beneath them.

Then, in the night, close beside them and just outside the pilot-room glass, was a quick glow of red. The plane lurched and staggered. Smithy clung desperately to the seat ahead. The pilot was fighting madly with the wheel. The roar of bombs from astern, where the bombers had launched their missiles at the approaching hill, was unheard. In a world suddenly gone chaotic he could hear nothing. He knew only that the valley dead ahead was whirling dizzily that it sank suddenly from sight.

They were crashing. That red glow they had been hit. Then something hard and firm was pressing against him, pressing irresistibly. It was the last conscious impression upon Smithy’s mind.