On and on, over pale gray wastes, above fleecy clouds and heavy fogs; high up over tossing waters, and floating mountains of ice—not a stop for fuel, with engines silenced until they flew like bats in the night, the Greyhound leading the way, and Epworth sticking to it like a dark, hungry shadow with his ship lines camouflaged by sky blue paint, and his eyes ever vigilant.

How Billy managed to keep the three red lights going notwithstanding the fact that he was a captive was a mystery that Epworth did not attempt to solve. It was being done, and Epworth was contented to follow.

At last Northeastern Siberia, and a mysterious range of mountains. Epworth, taking his position, knew them for the Cherski Mountains, recently discovered and completely unexplored—a barren, cold, lifeless region bordering on the Arctic Ocean a thousand miles from the outmost limits.

How long would this journey last? Where would the Greyhound lead? Had the sky bandits discovered that they were being followed, and were they leading him into a death trap amid a vast wilderness of ice?

He examined his gas supply. Joan looked at him inquiringly.

“Just about enough to take us back to Point Hope.”

Her eyes sought the cowling of the little machine fearfully.

“Shall we go back?”

She pointed at the Greyhound.

“Billy is in that ship,” she replied softly. “We cannot leave him. His liberty, and very likely his life, depend upon our actions.”

He put his hand affectionately on her shoulder—just like a chum. Few brothers loved their sisters as Epworth loved Joan.

“You are the bravest, squarest girl in the world. I knew you would say it. But——”

He shook his head.

“We will have to depend upon stealing enough gas from the tank of the Greyhound to get back,” she added smilingly.

Now the Greyhound turned abruptly westward, and followed the Cherski Mountains, lowering its altitude to five hundred feet above the highest peak. Epworth followed persistently, keeping a higher altitude.

“Small wonder,” Joan remarked as she watched the shadow of the Greyhound flit swiftly over the face of the white-capped ridges, “that the governments could not locate them. With their swift airplanes they dart down on the commerce of the world like Omar on a desert caravan, and are back in their hidden North Pole lair before the robbery is known by the authorities. Where are we?”

“Eight hundred miles north by west of Bogosloff Island, perhaps a thousand miles.”

“So far,” Joan observed patiently, “we have had unusually even weather. Now we are going to have an Arctic blizzard.”

She pointed north over the long reach of ocean that came up to lash the mountains beneath them. Epworth shivered. Then he smiled.

“We have a mighty staunch little airship.”

She did not answer for several moments. Would these bandits go on forever? Was there no hole anywhere for them to hide in?

“The Greyhound has disappeared,” Joan suddenly broke out excitedly. “I saw it just a moment ago behind that distant peak.”

Epworth glanced out of the window. A sudden sheet of frozen snow and a rain of heavy chunks of ice struck the window. It came with terrific fury, unexpected. However, he had adjusted the stabilizer, and notwithstanding the fact that the little ship was tossed up and down like a feather and went lop-sided for a second it weathered the furious burst, and staggered on like a wounded bird.

Epworth gave one more look for the Greyhound. Not a thing was now visible—not even the rugged snow mountains below. With a grave face he banked and faced the storm, putting on every ounce of power the engine would carry. The little plane stood still, poised like an eagle, with the bronzed shadow of its wings dipped in the immensity of gray storm and whirling, shrieking wind.

On the windows of his ship the rubber vacuum wipers stopped, choked immovable by lumps of ice hurled against the glazed surface. To see out was impossible—he was shooting through darkness, a howling, shrieking, terrifying murk created by storm. He glanced at Joan. She smiled at him to cheer him, but it was a courageous effort to conquer a mighty fear.

He must see out. If they moved forward in the direction they were headed they would be forced out over the ocean, away from the sky bandits’ retreat. That camp was somewhere in this range of mountains. He had a hunch that it was not far away. If he succeeded in his mission he must keep the mountains in view and make a search when the frenzy of the storm had passed.

Nevertheless he moved with slow deliberation. He pasted a small strip of inch-thick Balsa wood beneath the wipers on the window, lighted two candles and stuck them on the Balsa shelf thus made. It was dangerous—deadly dangerous. If the storm shot a flash of that blaze into the gas tank the end would be instantaneous. He smiled grimly, and nodded at his sister. The girl bowed her head in acquiescence. She also realized the danger of a flame of fire at this time.

The heat of the candles warmed the window and the wipers began to move, clearing the space for visibility.

His observations were useless. All he could see was a world of whirling snow and ice.

He sought altitude. But the higher he ascended the fiercer grew the storm. Then he nosed down slowly until he stood a thousand feet above the highest mountain. Then he slowed his engines and allowed the storm to push him backwards. He was seeking the neighborhood where he had last seen the Greyhound.

Again he turned his eyes on Joan. She was taking the battle like a Trojan.

“You are very brave,” he said gently.

“And the boy with me is not a coward,” she replied softly.

She gave him her hand, and there was not a tremble in it.

“I have lost our reckoning, but——”

The sentence was not completed. The tempest increased with irresistible fury, and shot them down obliquely, catching the starboard wing, and with weird, demoniacal power whirled the plane over and over in a rush of air that the propellers were unable to stop.

Joan was hurled into Epworth’s arms, and both were tossed up and down in their seats, and against the light cowling. Each second they expected to be hurled out of the cabin. In order to lessen the danger Epworth shut off the engine. At least there would be no fire.

“We must jump,” he explained briefly. “The plane is whirling over and over and will strike a peak soon.”

“Small chance for an umbrella in a storm like this,” Joan returned quite calmly. “It will be whipped into strips.”

“Yet the parachute is our only hope.”

He hooked the package around her shoulders and adjusted it carefully. Then he put one around his own shoulders, and handed her a package that he took from a pocket in the fuselage.

“Some useful articles, and a little food and water,” he informed her. “May come in useful. We can’t tell what is ahead of us.”

“Good bye, sister.”

“Good bye, brother.”

They smiled at each other, and jumped.