"She's in pretty good shape now, although not capable of the trip back to Earth."

Captain Linet entered at that moment, and with him Professor Erickson.

Holden recounted his adventures of the last hour and then set forth his plan.

"The cave is walled up with thin plating from the ships the pirates have brought in here. The entire gang is at work, repairing their own flier; none of them, or at least only a few, are wearing s.p.a.ce suits. I propose to drive the bow of the _San Francisco_ into the wall of their cave, previously weakening it by a few bursts from the _hexoxen_ guns!"

"It is possible," replied Edwards, "but it will probably put us out of commission altogether."

"In any case," put in Erickson, "we will be rid of this d.a.m.nable shield, and can communicate with our companions."

It certainly was the only plan, for, as soon as the pirates had repaired their ship, another unequal battle would be waged, with the result very little in doubt.

All hands set to work completing repairs on the main stern tubes, the only ones necessary to drive the _San Francisco_ forward. In less than three hours, Edwards p.r.o.nounced the work done to his satisfaction.

As the light began to creep in toward the base of the cliff, the huge ship rose slightly off the ground, the tubes glowed red and, guided by a powerful searchlight installed on the bow, Edwards pointed his craft toward the gleaming metal patch that marked the position of the pirate cave.

At short range, Holden, Linet, and Erickson opened with the three _hexoxen_ guns. They saw the bursts take effect on the metal. Edwards turned the power on full, and they felt the floor leaping under them.

Would the bow of the _San Francisco_ hold? Would they all be crushed to death at the impact? Another moment would tell. Holden saw the metal plates dead ahead, could distinguish the seams marking the air-lock.

He fired one final shot, and flung himself to the floor of the pilot room, endeavoring to find some means of bracing himself for the shock.

Then it came! Torn from his position, he saw the plates buckling and heaving about him. The lights went out. A great crash sounded in his ears, and everything went black. In a moment he regained consciousness, and staggered to his feet, bruised and dizzy. Thank G.o.d, his s.p.a.ce suit had not been harmed! A faint glow from the outside made things visible and he saw that the shock had torn a huge piece out of the plating of the pilot room.

A hand clutched his elbow, and through the phone in his s.p.a.ce suit he heard Linet's voice.

"Erickson and Edwards are knocked out. Let's see what we did to these chaps here."

Rushing back through the corridor, they collected as many of the crew as were able to move, flung open the heavy doors of the air-lock, and scrambled down to the floor of the cave.

Here and there lay bodies, pirates caught unawares. Suddenly Holden saw a blue flash. One of the mechanics clutched at his breast and fell, dead in an instant.

"Some of these fellows are still alive. They're using ray pistols,"

Holden shouted into his suit phone.

Even as he spoke he heard the sound of running feet from the darkness in the rear of the cave, where the bow of the _Silver Death_ was barely visible in her cradle, and in a moment at least fifty figures, pirates who had somehow escaped the fatal cold of s.p.a.ce, clad in clumsy suits and brandishing pistols, flung themselves desperately upon the smaller party.

Blue flashes were everywhere as the battle commenced, but the only sound was of struggling feet, with an occasional thud as a body hit the floor.

The pirates had been weakened by their long stay on the moon, and moved slowly, but the surprise of their attack, and the superiority of numbers had given them some advantage. It was man to man fighting, savage and merciless.

Holden, with a neat dive, knocked the feet from under a huge fellow who had trained a pistol on him, and they rolled over and over, each trying desperately to gain a second's advantage. He heard a dull crash to one side, as Captain Linet, jumping high into the air, landed with stunning force on a bewildered a.s.sailant. Thinking of Jean, waiting for him in some dim corner of the cave, he redoubled his efforts.

For a fraction of a second his pistol pointed toward his antagonist's body, and that was enough. He pressed the release, and the deadly ray shot into the body beneath him, dealing instant death. Freeing himself from the cold grip, he ducked an empty pistol flung at him by a new a.s.sailant. Again his finger bent, and another body dropped to join those lying motionless on the floor.

A fast-moving shadow caught his eye. He saw one of the pirates detach himself from a writhing group and head for the side of the cave. That was the place where Jean had said she would be waiting!

Pausing only an instant to make sure that his pistol was still charged, Holden sprang in pursuit of the fleeing form. He saw him stoop and pick up a heavy bar from the floor. The coward was going to burst open the chamber where the helpless captives waited! It was impossible to aim at that speed, so Holden forced his flying feet to move still faster, and foot by foot he drew closer to the man he pursued. Metal plates again gleamed in front of him, and he saw the pirate raise the bar high over his head, preparing for a blow which would crush the thin plates. The tiniest hole would mean death to the captives, who had no means of protecting themselves.

With one last desperate effort, Holden jumped, his Earth-trained muscles carrying him high into the air, while his pistol stabbed the partial darkness with vivid rays. Dodging and ducking, the pirate evaded the fatal stabs, while his bar beat a loud tattoo against the metal. Holden struck at him with his now useless pistol as he landed. The blow missed, and, losing his balance, he staggered and fell, past his foe, who quickly turned, raising his bar for a _coup de grace_ which never landed. The familiar flash of a pistol once more illuminated the scene, the bar dropped from dead hands, and Holden scrambled to his feet.

A voice was speaking through his suit phone, and he recognized it as Erickson's. "I just came to, tumbled out of that hole in the pilot room, saw the flash of your pistol, and here I am."

The old professor appeared, wobbling slightly, but still game. The flashes toward the mouth of the cave had grown fewer. Leaving Erickson to guard the compartment of the captives, Holden hurried back to the fight. Even as he went, the flashes died out altogether, and he heard Linet's hearty voice in the phone. "Holden, where are you? We've cleaned out them all down here."

Light was now flooding in from outside, and bodies could be seen lying thick on the floor, cold and stiff in death. Sadly Holden recognized many of them as his own men. After a hasty conference with Linet, he gathered together fifteen s.p.a.ce suits, and with an escort helping to carry them, he hurried back to Jean.

The door of the air-lock opened as his party approached. They went in, heard the swish of air entering, and in a few minutes the inner door swung wide. A happy crowd of men and women surrounded them, as they rid themselves of their helmets. Holden felt Jean's arms around him, her sweet lips once more on his. For a second they clung together, then parted, for there was work to be done. The s.p.a.ce suits were distributed and, as he led the way back to the _San Francisco_, Jean told him briefly the details of the long year of imprisonment.

"They gave us warning before they rammed us, as they wanted to save the women, for a purpose you can guess. Fortunately, there were never enough of us to go around, and these men, exiles from two planets, were always quarreling among themselves, so we were quite safe. We just existed, praying that some exploring expedition would find us, or that the _Silver Death_ would meet a ship too strong for her to ram and, fleeing here for refuge, be trailed."

Holden sighted Captain Linet hurrying toward them. In the light now flooding the entire cavern, he could see lines of despair and hopelessness written over the florid face.

"What's the matter?"

"Matter enough," came the ominous answer. "The s.p.a.ce phone on our ship is entirely disabled. We won't be able to get in touch with the _Ganymede_ or the _Los Angeles_. In a few days, the _hexoxen_ charges they plant will commence to go off, and that will be the end of us."

Holden stopped, stunned by the news. Fleeting visions of happiness with Jean vanished into thin air. He would be destroyed by the chemical he had invented, with which he had hoped to save the world.

"I thought we might get out in the _Silver Death_," continued the captain, "but the entrance is entirely blocked by our own ship, and I'm afraid it will never move again."

Then Jean's clear voice cut in. "How about the s.p.a.ce phone on the _Silver Death_? Won't it work?"

"Why, of course it will," laughed the captain, amused at his own stupidity.

Stumbling and tripping in their haste, the three hurried through the open air lock of the pirate craft, into the pilot room.

Holden feverishly set to work, whirling the strange dials, pushing this b.u.t.ton, then that. At last a faint roar sounded in the loud speaker.

Pressing his helmet against the transmitter, so that the vibrations would carry his voice, he shouted, "_Ganymede_, _Los Angeles_, Holden calling."

"What ho?" came a cheery voice, which he recognized as belonging to Huges, commander of the _Los Angeles_.

Breathing a sigh of relief, he explained the situation. Busy days followed. _Hexoxen_ and Europium from the _San Francisco_ were transferred to the other ships, with as much of the treasure collected by the pirates as could be loaded into the cramped quarters.

With Huges and Rogers a.s.sisting, Holden revised the schedule for planting the charges.

"We simply haven't time," he explained, "to set the charges as close together as I had planned. There's nothing to do but get all of them in that we can, and then hope that conditions in the interior of the moon will be of a nature to promote the action of the _hexoxen_."

The ships' crews understood only too well the importance and danger of their work, and during the days that followed they toiled like a gang of madmen. Parties raced each other over the rough surface of the dead satellite, grimly determined that their efforts to save the world should not be in vain. Even the men of the party which had been rescued, weakened as they were by their long stay in the pirate cave, insisted on giving what help they could.

Finally came the day when the first charges were set to go off. Holden sat in the pilot room of the _Ganymede_, his eyes on the chronometer, while Captain Linet swept the desolate plain with powerful binoculars for the cloud of dust which would signal the return of the last party.

"Five minutes yet, Captain," Holden said in a low voice. "Tell the _Los Angeles_ to pull out. The first charges are scarcely two hundred miles from here, and I'm not certain how fast the reaction will travel."

Five minutes. Two minutes. The silver shape of the _Los Angeles_ was already fading in the distance. Suddenly a sharp shock rocked the stony bed on which the _Ganymede_ was resting. Simultaneously five figures appeared, racing at full speed for the ship. Shock after shock tore at the ground beneath their feet. Holden stood at the controls, waiting for the signal that his five comrades were safely aboard. To his tensed nerves it seemed hours before the welcome sound came to his ears, and with a sigh of relief he opened the power into the stern tubes, and laughed happily as the huge ship shot away from the heaving surface of the dying moon.