Chapter I

"_O Moon of my delight_
That knows no waning..."

Terra--19th Century.

In the semi-darkness, the vast crysto-plast observatory was deserted. For the fifteen Tiers devoted to the feast, overflowed with celebrants who observed the three hundredth anniversary of their landing.

All Io seemed devoted to the chief preoccupation in their lives, and, had managed to make of an historic fact, the excuse for a planet-wide bacchanale. Julian Varon removed his black silk mask and stepped to the wide balcony overhanging the plains. The frosty air was like a benison on his narrow, high-cheek-boned face, and the silence was a greater blessing still. Vaguely, he remembered the lines of an ancient poem of the twentieth century, which, by one of those ironies of Fate, had been preserved when far greater masterpieces had faded into oblivion:

"_The brandy's very good--
Blue space before me and no sign of man._"

Meditatively, he raised the fragile Bacca-glass to his lips and sipped the fiery liquor that Ionians distilled from the fragrant stems and leaves of the _Clavile_ plant. For days, his mind had whirled in hopeless circles, and he wondered with a curious sense of detachment, whether he wouldn't be better off to leave the problem to the scientists. Only, it was his duty as much as any scientist, to search for clues.

Julian raised his eyes and gazed at the great tiers of stars that glittered above the towering, purple crags of the _Mallar_ range. Throughout the hours of the Ionian night, the skies had been peopled by the singing of these constellations. But there had been none to hear it, for despite the ravages of the _Silver Plague_, the inhabited Moons of Jupiter had gone mad with revelry, as if they would distill the last drop of pleasure from each passing hour that brought them closer and closer to extinction.

"I wonder," Julian spoke aloud, "why decadence always hastens the tempo of pleasure!" He smiled acidly as his own voice sounded strange in his ears. Below him, the blazing tiers within the transparent enveloped, that was Atalanta, capital of Io, the great Galilean satellite, sparkled polychromatically in the night. In the utter silence, a stream of music faint and far away, like a tiny goblin orchestra reached him, as the icy wind plucked with elfin fingers at his cape.

And something else reached him, too, that sent the blood racing through his veins as his hypersensitive awareness of danger, translated the sound of stifled breathing behind him into a signal for action.

He whirled with a speed that was an index of Jovian training, for in the vastly lighter gravities of the Moons, his muscular coordination was breath-taking.

Before him stood a Mutant in the act of crouching for a leap. He was huge, squarely built, his silver mane standing straight out as he sprang with a murderous rush. Julian stepped aside with calculated ease and his left hand moved like a piston into the Mutant's face. There was no time to seek the hidden "electro" under his arm-pit, and power-rapiers had to be checked before entering pleasure palaces. The Mutant bellowed with fury, and rammed a right deep into Julian's ribs, then brought up his left and Julian tasted the claret in his mouth. The silver-haired, silver-eyed being was obviously fighting to kill. And suddenly Julian's vast amazement changed to a cold fury that turned his blue-grey eyes to a smouldering black.

He slid two sharp jabs into his enemy, then crossed his right and felt bone give under his fist. He moved in, blasting with both fists like rocket exhausts, and heard the Mutant's breath exploding from his body. The Mutant with supreme effort tossed a fist grenade at him, but Julian had caught the rhythm of the battle and swayed away with it; he made the assailant miss again, then with all his dynamic power sent his right hand crashing home.

He saw the Mutant, face askew, slide drunkenly to the blood-patterned floor. Then cool hands were on his wrists, on his brow, and sanity began to return again.

"Darling!" Narda said in a husky voice that was distilled music, and drew down his golden head against a priceless gown that was all blue shadows and pin-points of lights, to stanch the blood from his cut lips. Her violet eyes were bright with unshed tears, but in the odd, slurred melody of her haunting voice there was no tremor as she asked, "What on Io's happened? Were you recognized by any chance? _And a Mutant...!_"

"Hardly think so ... still.... Oh, forget it, this is not a night for problems. Did anyone ever tell you that your eyes are in Heaven," he grinned irresistibly with a charm that made him seem younger.

"No! None of your ... what was it your barbaric ancestors called it?... _blarney!_" It was then she noticed the tell-tale silver flood at the roots of his yellow mane, and her heart stood still. _The Silver Plague!_ Carefully she lighted a cigarette and blew a perfect smoke-ring into the icy air, she brushed an imaginary tobacco speck from lips that were like red roses. And when she spoke Narda was perfectly calm.

"I came to find you because they're going to play the _Ecstasiana_ with a native orchestra from Ganymede--the muted viols and flute-like instruments, and those weird violins of that strange race.... We danced it the first time we met. Remember, my dear?" Her eyes were radiant as if all her tears were concentrated in her heart, leaving only their sparkle behind.

* * * * *

He nodded silently. He was too full of the racking knowledge that all his dreams had been destroyed by this alien malady that turned the hair to gleaming silver, and rendered them sterile. That, and his terrible love for this exquisite, gallant being who had consecrated her youth and brains and loveliness to the only ideal in the chaos of their lives--The _Dekka_. And as they turned to go, the tiny tele-rad on Julian's wrist began to flash a pin-point of light in a complicated code.

They both watched instantly alert, translating the urgent message with the ease of years of experience. The message was peremptory--final. They were to repair to the Dekka's ancestral Hall without delay for a plenary session. The laconic order ceased as the instrument went blank. Julian Varon looked at Narda for a long moment. Then he shrugged his shoulders. "We'll have to leave right away, it may be _emergency_!"

Narda nodded. "We'll have barely time to change in the spacer."

From below, the strain of the _Ecstasiana_ rose to engulf them in a flood of melody.

She laid a sculptured hand on his arm. She was silent. She was waiting. The _Dekka's_ summons brooked no delay. For this was no game of mere intrigue, but a gigantic fight instinct with the overwhelming drama of the unseen. The huge Mutant on the floor groaned and rolled to one knee. He had the strength and courage of a _Felirene_. He got up and rushed with scorn and hatred written on his features. He came with all rockets firing. Julian stood there in the battering storm and fought back. He dug his left into the flesh of the Mutant inches deep, then ripped a hook to his jaw. In the clinch that followed he could hear Narda's sobbing breath, as the Mutant's laces pounded low; he countered with secret, murderous tactics of his own. Then, he pulled the trigger on his left hand, aiming with precision at a vital spot. He let it go. He heard the Mutant crash against the floor and lay still. Julian stood for a moment with his tongue on fire, his lungs heaving like bellows with the effort. He bent down and forced himself to search the man, but there were no clues on the giant.

* * * * *

From above, Atalanta was like a gargantuan bottle left behind by some god in his cups. Narda at the controls brought the intra-Moon spacer spiraling down expertly to a landing behind a concealing rampart of rock. Ahead of them a black, basaltic cliff reared its jagged crags, its boulder-strewn base seemingly impassable. Nevertheless, the two masked and cloaked figures hurried their steps toward the desolate barrier.

"We're probably late!" Julian observed. "We seem to be the last to arrive." He drew his dark, _Felirene_-lined cloak closer about him and led the way forward.

"Small loss if we've missed the preliminaries!" Narda replied. "I wonder how much longer the _Dekka's_ going to wait? For fifty years Mutants have been appearing in our midst in small numbers--changed overnight, rendered sterile--and the scientists did nothing about it. Lately it has become a plague that threatens the Moons with extinction, and still we're fumbling in the dark! Oh, Julian!" Her voice rose in an ascending scale of grief.

"Don't move!" Julian whispered harshly and froze into immobility. He'd detected motion--something that had stirred among the boulders to his right. Instinctively his fingers groped for the handle of the tiny weapon under his arm-pit. No bigger than a toy-gun, its electronic stream was devastating at close quarters. He aimed it at the spot where he had sensed movement and fired as a darker shadow catapulted out of the gloom.

The spectral-blue beam of radiance from the weapon met the creature in midair and melted a jagged hole in its side; there was a fiendish scream of agony, then briefly a muffled tumult among the boulders.

"What on Jupiter was it?"

Narda stepped forward to investigate, but Julian stopped her. "No time now." It mattered little what manner of beast had waylaid them. The Jovian satellites, even frigid Callisto, had teemed with life of their own before colonization by Man. And, since the Terrans had preferred to build stupendous cities within transparent, berylo-plastic shields, shaped like bottles, there had been small point in the systematic destruction of native fauna. The cities were largely self-sustaining, anyway. All commerce and intercourse was carried on by air. Only adventurers and fools would venture into the wastelands ... adventurers and fools, and perhaps, members of the _Dekka_.

As they reached the base of the cliff, Julian glanced back at Narda and smiled. "Be alert, I'm forcing issues tonight ... inaction's killing me!" He was like a Martian eagle--poised for battle.

Narda sensing his mood smiled thinly in the shadows.

She wondered silently what new, macabre mission would be assigned to them this time. And hoped that the summons meant something far more than the usual battle between rival Societies striving to milk the venom from each other's fangs. For on at least three major Moons, Io, Europa and Callisto, men and women were struck by an invisible foe that left them trembling with fever, and when that dwindled away, a tide of silver rose from the roots of their hair, and even the eyes became luminous with the deadly patina. Nothing was known of Ganymede. It was hard to tell in the absence of reports, for Ganymede, aside from its own native civilization, had been colonized by Terran Mutants, who could and did procreate, thus perpetuating their race. But the victims of the Silver Plague were left sterile. It was hard to differentiate. Meanwhile the Moons were dying!

And yet, a stubborn feeling in her heart kept insisting that perhaps the _Plague_ was something man-made, and like all poisons should have an antidote. She glanced at Julian and shuddered with anguish--there would be no progeny for them--her own turn might be next! What a fiendish weapon, if _it was a weapon_, she thought. The ultimate in refinement of warfare--a refinement that in their Moons had been going on for three hundred years!

* * * * *

Narda shivered again, increasingly cold, as she let her mind rove briefly over their past history and their centuries of spurious peace. For nothing as crude as open, physical warfare disturbed ever the equilibrium of the various Moons. On the surface, the various governments maintained the most cordial relations--idyllic almost. But underneath--that was a different story! The most ruthless strife had never abated for even an hour. It might take the form of secretly systematic destruction of vibroponic farms of a world desperately in need of food; or perhaps the categorical embargo of essential supplies non-existent in another Moon. Or the proselyting of vast members of colonists from a sister world by means of economic lures. The loser always paid enormous ransom in whatever it was the victor coveted.

Thus the subterranean warfare was carried on by secret Societies, much as hitherto the Ancients on Terra had employed secret agents, members of the powerful "Intelligence." Only that on the "Moons," the Societies had much greater power than the _laissez-faire_ governments themselves. Each Moon had its "Society," disavowed, legendary, invisible. They maintained secret armies of Astro-operatives and space navies always in readiness for _any_ eventuality--or an initial _open_ break that none of them had the courage to be the first to start. But more important still, in their vast, secret laboratories, armies of scientists and technicians toiled ceaselessly on new techniques and inventions. Delved into intricate psychological data that was a miracle of ingenuity, calculated always to prepare as far as possible against the _unpredictable_.

The murmuring wind of Io swirled among the stones and laved them with its icy caress, and Narda trembled violently again. This time the spasm failed to abate, and she whispered through chattering teeth:

"Please, Julian ... hurry. I'm chilled to the marrow ... d-dear...."

"You're what?" His voice was suddenly a rasping in his throat.

Julian straightened slowly from where he kneeled at the base of the cliff, where he'd been activating the mechanism of the concealed entrance with the wrist transmitter. He eyed the convulsed form of Narda then touched her burning forehead; he noted the tendons corded at her throat. A cold sweat of anguish beaded his brow as he said casually, "It is cold, darling," and then he punched carefully, precisely, and cried with agony as he felt his hand touch her flesh. He caught her tenderly as she slumped in his arms without a sound. He kissed her cold cheek and sought consolation in the fact that she would not suffer the first harrowing convulsive fever of the Plague. It would last for two hours. _How well he knew from experience the course of the disease!_ And he hoped Narda would not come to before then.

Quickly he retraced his steps to where they had left the ship, and deposited her inert form in the control room. Then he prepared a note which he placed in her hand, it read: "_It was the kindest thing to do, darling. Wait until I return. There's hope._"

He finally adjusted the wrist-transmitter to the exact wave-length required to open the entrance to the _Dekka's_ Hall of Sessions, raced swiftly toward the cliff like a disembodied shadow. In the distance a golden _Felirene_ wailed its banshee love-call, urgent, savage--as savage as the burning agony that stifled Julian's breath, and as primordial.