A rock loosened by his flying feet rattled and pounded down the hillside. Instantly the monsters whirled round, sighted him and started in pursuit. With a mighty leap he cleared a ten-foot ledge, carrying his unconscious burden, and plunged into the sheltering mist of the clouds. Up, up! Thank God for the weak gravity!
A swishing rattle of claws on rock shot by them in the fog, turned and swept back. Penrun sprang straight upward, rising nearly a dozen feet in the air as the monsters streaked past underneath.
Only a little farther! Savagely he forced his failing strength to carry them up the slope. The air was chilling fast and the mist thinning. He broke into clear air as the fog behind them filled with the rattle of racing claws on the barren granite and the grating roar of the baffled monsters, seeking frantically for their intended victims.
He staggered on another hundred yards before he collapsed with lungs laboring desperately in the rarefied air.
Below them a bristly monster charged out of the fog, sighted them lying up among the rocks, and leaped after them. Penrun jerked up a pistol with trembling fingers and loosed its deadly ray. The huge spider stumbled and ploughed head-on among the rocks with a flurry of legs. It rose loggily, for its fierce energy was dwindling rapidly in the biting cold. Again the pistol crackled. The gigantic insect toppled over and rolled down the mountainside into the fog and vanished.
"Are we safe now?"
Penrun turned. The girl was now sitting up somewhat unsteadily, with an ugly bruise on her forehead.
"I think so," he replied. "Up there in my space-sphere we shall be quite safe."
Together they plodded silently up the sharp incline of the peak, her hand in his. And as they went he marveled that her eyes could be so beautiful now that the fear and horror had vanished from their depths.
The storm clouds below had broken up and dissolved under the increasing heat, revealing the Trap-Door City, seemingly deserted, and the motionless black ship still resting on the plateau. Penrun turned to the girl beside him in the control nest of the space-sphere.
"What are your friends waiting for all this time?" he asked abruptly.
"They're not my friends," she retorted. "And you might have guessed that they are waiting for you to arrive with the other third of the map. They are planning to surprise you and rob you of it. The entrance to the Caves is under the edge of the Cataract over there, and by waiting here they are sure to be on hand when you arrive. Only"--her brows puckered in a little frown--"I don't understand why they remain out there on the open rock after Helgers has picked a hiding-place for the ship."
"He is the leader of the gang, and he is the man who killed that poor old Martian aboard the Western Star for the map. Helgers learned about the treasure and the existence of the map through a convict who was with Lozzo in the prison. Helgers pretends to be an importer in Chicago--he actually owns a nice little business there--but in reality he is one of the biggest smugglers in the Universe."
"How do you come to be with him?"
"I was coming to that," she replied. "My parents live on Ganymede."
Penrun nodded. He was familiar with the fourth satellite of Jupiter and its fertile provinces.
"My father is an American, but my grandfather on my mother's side was a Medan nobleman. He was ruined by that notorious pirate, Captain Halkon, who descended with his ships on our city and carried off everything of value, including the vast amount of scrip credits owned by the state which were entrusted to my grandfather. You know the Ganymedan debtor's law?"
He did indeed! It was one of the most infamous laws of the Universe: ruling that the debts of the father descended to the children and their children's children until paid.
"My family is now poor," she went on. "For a century or more we have striven to pay off the debt caused by the loss of those state funds. That's the way matters stood when I received a letter from my brother Tom in Chicago, who was employed in the office of Helgers' legitimate importing business, little aware of the smuggling. Tom had somehow got wind of the near discovery of Halkon's treasure, and I saw a chance to get a part of it by joining Helgers' party. He might not want us, but he would be practically forced to take us to keep our mouths shut. I felt that we were honestly entitled to a part of that treasure which had been stolen from our family, and with it we could pay off that old debt that had ridden our family like an Old Man of the Sea for more than a century.
"Getting into the expedition proved much simpler than I had expected. When Tom told Helgers about me he was very eager to help us--he is one of those men who is always anxious to help a girl if he thinks she is good-looking enough. So you see when I held you up in your stateroom I was merely performing my part of the scheme, although I didn't know then that Helgers had already slain the old Martian and leaped out into space.
"After that the Osprey--the ship down there on the plateau--overhauled the Western Star and took us off, and shortly afterward I learned most unpleasantly that Helgers had no intention of giving Tom and me our share unless I gave myself to him in exchange. I told Tom, and trouble started. It came to a head yesterday and there was a fight and--and Helgers killed Tom."
She began to weep quietly. Penrun stared grimly down at the black, motionless ship. Presently the girl resumed her story.
"I managed to get the air-lock open and escaped from the ship. Then that horrid spider caught me. You know the rest."
Her voice trailed off. Penrun remained silent for a while.
"You haven't even told me your name," he reminded her gently.
"Irma Boardle," she replied with a wan smile.
"I am Dick Penrun, in case you don't already know me. Captain Halkon was my grandfather. We always tried to keep the knowledge of it a family secret, since we were ashamed of it. If I--we get our hands on that treasure, I can promise you that the debt hanging over your family shall be paid first, Miss Boardle."
"Not Miss Boardle. Call me Irma," she said, the wan smile growing suddenly warm.
Penrun looked at her thoughtfully.
"But we aren't near the treasure yet," he said. "Between the spider monsters and the human monsters in the ship, our chances are rather slim. We'll just have to wait until we get a break."
As the day wore on there was a note of menace in the silence that hung over the Trap-Door City. It was nothing tangible, unless it was the appearance of two long silvery rods mounted on the top of the huge cocoon-palace of the Queen aiming down at Helgers' ship. Penrun could have sworn they were not there yesterday. The sight of them made him uneasy.
Helgers must have interpreted the silence differently, for presently a man emerged from the ship, protected against the heat by a clumsy space-suit. He hesitated, then walked slowly away from the ship, and paused again, waiting for the spiders to attack. Not a movement was made in the city. Presently he moved on again toward the cataract which had dwindled in the heat of the day to a mere trickle of hot water down to the pool in the gorge more than half a mile below.
After a time the man reached the cataract. He descended the short path that led down under the lip of rock to another ledge a few feet below it. The entrance to the Caves opened out onto this lower ledge. Little wonder, thought Penrun, that no one knew where the Caves were.
Some time later two other men from the ship followed him.
"Fools!" muttered Penrun, following them through his glasses. "They think the spiders are afraid of their ray artillery. I'll bet the monsters are either waiting until all the men wander out of the ship, or else they're getting ready to spring some hellish surprise."
Other men came out of the ship, carrying rock drills, a roll of cable and a powerful little windlass. Instead of going to the Caves, they went round the ship to the other side under the doubtful protection of the ray-guns, and sank two shafts into the granite. Into these they drove steel posts and anchored the windlass. One end of the cable was attached to the windlass and the other to the nose of the ship. Then they slowly dragged the big craft across the plateau on rollers from the ship's store room.
"That's strange!" exclaimed Penrun. "The ship can't rise! I wonder what's wrong, and why they are pulling it away from instead of toward the Caves."
"I don't know what's the matter with the ship, but I believe I know why they are moving it," volunteered Irma. "They're taking it to that hiding-place I told you Helgers picked out--there behind that upthrust of rock. You see, they think you know where the Caves are because you have explored Titan, and they think you will come directly here, so they want the ship hidden to make sure you land."
Half a hundred men in their space-suits toiled like ants about the big cylindrical craft until they at last jockeyed it into position behind the natural screen of rock. Even before it was in place other men were swarming over the ship with paint machines, coloring it a granite gray. When they had finished the ship was nearly invisible from the sky.
Penrun paid little attention to their preparations. His attention was centered on those two shining rods atop the Queen's silken palace. They now aimed at the ship in its new position. A strange idea flashed through his mind. Those rods had in some mysterious way put the elevating machinery of the Osprey out of commission!
Suppose the spiders turned them next on his own space-sphere up here on the peak? The thought sent a shudder through him. Visions of the final flight across the nightmarish, distorted granite, the running down and capture of himself and Irma, the paralyzing bite of the monsters in the cavern of the Living Dead flashed across his mind. Cold sweat stood out on his forehead. Instinctively his hand leaped to the propulsion control and hovered there.
Yet why hadn't the spiders attacked the ship, now that they had it helpless? It was not their usual tactics to give their victims a chance to free themselves. Why, why? There could be only one answer. They were waiting for something! Penrun's eyes glinted suddenly.
"Irma," he said rapidly, "we are in serious danger. The spiders have obviously put the elevating machinery of the Osprey out of commission. Helgers and his men are doomed to the Living Death as surely as though they were already lying in the silken hammocks. If the monsters choose, they could do the same thing to our sphere and doom us to the same fate. I believe they are waiting for something. While they wait we have a chance to get the treasure and escape. Shall we risk it, or shall we go while we know we are safe?"
She looked up at him evenly.
"If you think we have a fair chance to get the treasure and escape, I say let's risk it," she said firmly.
"Good!" he exclaimed. "Here we go!"
The little sphere slipped out of its cleft in the peak and dropped swiftly into the valley on the side opposite the Trap-Door City and its mysterious menace. Day was swiftly dying, and the lower passes of the mountains were already hazy with rapidly forming storm-clouds.
"Look!" cried Irma excitedly. "What are those things?"
Far in the distance a long line of wavering red lights snaked swiftly through the dusky valley toward them. Penrun picked up his binoculars.
"Spiders," he announced. "Scores of them. Each is carrying a sort of red torch. I have a feeling that those are what the monsters of the Trap-Door City have been waiting for."
He urged the sphere to swifter flight along the range. Miles from the Caves, he swept up over the peaks, and dropped down on the lowlands side. Dusk was deepening rapidly as he raced back toward the White River cataract under the pall of the gathering storm.
Among the boulders on the rough mountainside near the mouth of the Caves he eased the craft down to a gentle landing.
"Wait here," he told Irma. "I'll investigate and see if it is safe to enter the Caves."
They had seen the three men return to the ship, but others might have gone to the Caves after that. Penrun made his way down the slope to the lip of the cataract and the yawning blackness of the abysmal gorge below it.
Overhead the storm was gathering swiftly, and the saffron light of the dying day illuminated the plateau eerily. Half a mile away the Trap-Door City shimmered fantastically in the uncertain light. Penrun repressed a shudder. The Devil's own playground! Thank God, he and Irma would be out of it soon!
He crept down the narrow path that led under the ledge of the trickling cataract. Outside, a bolt of lightning stabbed down from the darkened heavens. Its lurid flash revealed the huge figure of a man, pistol in hand, beside the entrance to the Caves.
Too late to retreat now, even had he wished to. Penrun's weapon flashed first. A scream of pain and fury answered the flash, and the man's pistol clattered down on the rock. The next instant Penrun was helpless in the clutch of a mighty pair of arms that tried to squeeze the life out of him.
"Burn, me, will ye, ye dirty scum!" roared the giant of a man tightening his grip. "I'll break your damned back for ye and heave ye into the gorge!"
Penrun writhed frenziedly, trying to twist his pistol around against his enemy's back, while they struggled desperately about the ledge above the dizzy blackness of the gorge. But the pistol struck the wall beside the entrance and fell under their trampling feet.
Penrun was gasping in agony at the intolerable pain in his spine. Darting points of light danced before his eyes. Then from the opening in the rock showed a beam of white light and a man slowly emerged from the Caves. The grip on Penrun relaxed slightly as the man came toward the two combatants. Penrun could distinguish him closely now. A heavy, pasty face with liquid black eyes and a crown of thinning hair. Helgers! He was staggering and grunting under the weight of a heavy metal box.
"What's the matter, Borgain?" he asked.
"Got this bird, Penrun, we been waitin' for!"
"We don't need him, now that we already have the treasure. Still, it's a good thing we found him. Just as well to have no tales circulating about the Universe about our find. Toss him into the gorge, and go down and watch the other three chests until I get--"
"Dick, Dick!" Irma's excited voice floated down from up among the boulders. "The spiders with those red cylinder torches have arrived! They are attacking the Osprey!"
Helgers jerked up his head.
"Why, if it isn't the little spitfire!" he exclaimed in pleased astonishment. "I thought the damned spiders had eaten her long before this. Rather changes things, Borgain. I'll just go on up and let my little playmate know I am here. Toss our friend over the edge there, and bring up another treasure chest."
"What was that she was sayin' about the spiders attackin' the Osprey?" Borgain's voice was anxious.
"Oh, that's nothing the boys can't handle," said Helgers confidently. "In case they don't, we'll have to feel sorry for them and take our friend's sphere. Only have to split the treasure two ways, in that case," he added, moving up the slope.
Borgain's answer was a grunt of surprise, for his captive had squirmed suddenly out of his clutch. The big man plunged forward recklessly with arms outstretched in the groping darkness. Penrun, desperately remembering the sickening drop at their feet to the pool three thousand feet below, backed against the rock.
A flash of lightning. Borgain's ape-like arms were nearing him. Penrun lashed out at the darkened features. His knuckles bit deep into the flesh. He slipped aside as Borgain, mouthing fearful curses, rammed into the rock wall and rebounded.
Again the fumbling search. Another lightning flash. Penrun struck with frenzied desperation. Borgain took the blow behind the ear and staggered. He whirled, wild with fury, and charged vainly along the narrow ledge.
"I'll get ye this time, damn your dirty carcass--ugh!"
Guided by the sound of his voice, Penrun struck with all his strength. Borgain's nose flattened under the blow. He whirled half around.
"I'll kill ye! I'll kill--help, help--a-ah!"
Lost in the blackness he had plunged over the lip of the rock, thinking he was charging Penrun. Down into the yawning gorge his body hurtled, the sound of his frenzied, dwindling screams floating up eerily out of the black, ominous depths.
Penrun crouched against the wall, sick and trembling. Irma, Helgers! He must hurry! He fumbled again for the pistols. They were gone. Crawling forward now, still shaken by his narrow escape from death, he gained the pathway. The rain was drumming wildly on the barren granite now, and the pitch-blackness was shattered only by ghastly lightning bolts.
Guided by the flashes, he clambered up the slope and halted abruptly. The door of the space-sphere was open, and, silhouetted against the soft glow of light within it, was Irma, seated dejectedly with bowed head, heedless of the cold rain beating down upon her. Helgers was nowhere to be seen. Penrun dashed forward.
"Irma, Irma!" he cried. "What has happened? Where is he?"
She raised her head slowly and stared at him as at one risen from the dead. Then she burst into tears.
"He said they had killed you--had thrown your body into the gorge," she sobbed. "I--I just didn't want to live after that. Are you hurt?"
"Not a bit," he assured her fervently. "But where is Helgers?"
"I pistoled him," she said quietly. "I had no choice. He came at me after I warned him to keep away. He fell over there among the rocks. Oh, Dick, let us hurry away from this mad place!"
He stared at the rain-swept rocks. The heavy metal treasure chest lay a few yards away where Helgers had dropped it. Penrun moved cautiously toward the spot where he had fallen. He was gone. The rain had washed away any traces of blood that might have remained.
While Penrun hesitated, the roar of the tempest was split by a man's scream of agony. A lurid flash of lightning an instant later revealed a gigantic spider down by the cataract with Helgers' struggling body in his mandible jaws. Returning blackness blotted out the scene.
Irma's pistol stabbed a ray through the driving rain at the hideous monster. Instantly its grating roar for help rang out, and a group of red lights from the doomed Osprey across the plateau, detached themselves from the others and came streaking for the cataract.
Penrun seized the heavy treasure chest and staggered to the sphere.
"Hurry, here they come!" screamed the girl.
He fell through the door with his burden just as the foremost monster leaped the river. The next instant Irma sent the sphere rocketing upward. Just before they plunged into the clouds they caught a last glimpse of the Osprey with her ray guns melted off by the red cylinder torches, and great holes gaping in her sides through which the monsters were carrying out the members of the crew to their cavern of the Living Dead.
As the sphere burst through the storm cloud into the frigid air above it, Irma gave a cry and pointed at the peak where they had hidden in the sphere. The peak was now alive with moving red lights of monsters searching vainly for them. The scene dropped swiftly below as the sphere gathered speed for its homeward journey.