AT LEAST A THOUSAND generations ago, Kremastor began, shortly after his ancestors had discovered a form of warp drive, they stumbled across the nexus system, just as the Enterprise had. They also found the "maps" early on during their exploration of the system, but in their case it was apparently a complete set, not just the "local" ones that so far had been fed into the Enterprise computer. The maps showed that the system consisted of a series of approximately a hundred nexus, each of which was connected to every other nexus and to thousands of individual gates, one of which was the one Kremastor's ancestors had found approximately fifty light-years from their home world. The nexus themselves seemed to be intended primarily to serve as junction points for great numbers of individual gates, as the hub of a bicycle wheel serves as a junction for dozens of spokes. The nexus, however, were apparently accessible directly, and it was one of these, one of the most complex of the lot, into which the Enterprise had originally stumbled, only to pop out of another billions of light-years distant and almost equally complex.
Kremastor's maps were apparently more complete versions of those already in the Enterprise computer. Each nexus and each destination was identified by a code. Each nexus went through a continuous cycle, opening onto a different destination every few seconds. The times at which a nexus had to be entered in order to reach the various destinations were specified. No destination was more than a day distant, even if one had to pass through all hundred nexus to get there.
The set of maps Kremastor's ancestors were given told them how to reach any of more than a million individual destinations.
What the maps did not tell them was the location of any of those destinations with respect to any other destination.
As far as Kremastor's ancestors had been able to determine, not a single destination was anywhere within their own galaxy.
Nor could they discern the slightest pattern in the destinations. It was as if they had been picked at random from anywhere and everywhere in the universe. Of the destinations they explored, some were in the hearts of massive star clusters like the one the Enterprise had first been transported to. Some were in the deadly centers of galaxies that would have dwarfed the Milky Way. A very few were within light-hours of solar systems. Some were on the fringes of galaxies of all sizes. Many were deep in intergalactic space.
And a few—a very, very few—were like the one the Enterprise and all those other ships had found themselves ejected from. They opened on starless, lightless voids hundreds of millions of parsecs in diameter. A few opened on voids so huge that the entire universe seemed empty. No galaxies or stars were within range of the exploring ships' instruments.
For generations, Kremastor's ancestors had explored the nexus system. Just how many destinations they reached, he didn't know. The few surviving records didn't say, but it was obvious they could not have explored more than a few thousand of the more than a million destinations available.
Then, in a solar system only a few light-hours from a gate, they found the remnants of a civilization. It had destroyed itself in an atomic war thousands of years before.
Shortly after that discovery, ships began to disappear, to head out for new destinations and simply not return.
Finally, one of the missing ships did return, but all aboard it were dead. From what little Kremastor's ancestors could learn from the ship's fragmentary log, some form of insanity had come upon them as they emerged from the gate, and it had swept the ship.
Immediately, rigid quarantine procedures were set up. Because of the gate's distance from their home world, the quarantine worked, and when other infected ships returned, some with one or more crew members still alive, the home world remained safe.
Meanwhile, their scientists had been studying the gates, trying to measure and understand the forces that drove them. By the time the infected ships began to return, the scientists had succeeded to some extent in measuring those forces, even manipulating them, but they never came close to truly understanding them.
But manipulating them, it seemed, was enough, at least for the harsh but purely defensive measure Kremastot's ancestors devised. They were able to build the Trap and link it to more than half of the nexus. The Trap itself was a pure energy device that could reach into the limbo that surrounded the nexus, identify virtually any sentient being that had been infected, seize that being and all matter in its vicinity, including whatever ship it was traveling in, force it out through this or other equally isolated gates, and keep it from reentering. There, millions of parsecs from the nearest star, the ship would be in permanent quarantine. Even if the infected crews survived, they could not spread their infection.
Where the infection—the entities—came from, even what they were, Kremastor's ancestors had no way of knowing. Alone, they registered on no sensors, not even those of the Trap, just as they had registered on none of the Enterprise instruments, only on the minds of its crew. Only when one of the creatures attached itself to a living, sentient being could its presence be detected.
As a result, the Trap was far from perfect. As long as the creatures were not attached to sentient beings, they could roam the system freely, emerging whenever and wherever they pleased.
In the end, either the quarantine procedures that isolated the gate near Kremastor's home world, after generations of inactivity, grew lax, or one of the creatures emerged from the gate unattached and undetected.
Either way, the civilization of Kremastor's ancestors was infected and destroyed, just as that of the Aragos had been infected and destroyed thousands of years later.
But, like the Aragos, Kremastor's people had recovered. Over tens of thousands of years, they had made their way back to civilization, and they had found the records their ancestors had left behind, in permanent orbit around their home world.
And when they found those records, they had wondered: How many thousands of civilizations like their own had been destroyed by these creatures? How long would it be before, despite all their efforts, their own resurrected civilization would be destroyed once again?
So they decided: The only way to end the threat once and for all was to close down the system altogether. For another generation, then two, they studied the forces involved. Finally, though full understanding never came, they devised a way to shut the system down. They built a device that, once taken to the central nexus—the nexus the maps indicated was the source of the entire system—would be capable of destroying the system. When activated, it would literally turn the entire nexus system inside out, setting into self-destructive oscillation its still not fully understood energies. It was crude, the equivalent of Ensign Stepanovich's phaser blast in the Cochise engineering control room, but it was the best they could do.
And it would be effective.
But whoever undertook to use the device would, in effect, be going on a suicide mission. Even if he survived the action of the device itself—and he almost certainly would not—he would be trapped millions or billions of parsecs from home, with no nexus system to return through.
A dozen ships with the device were built and sent out, then a hundred. None returned, and the nexus system remained in operation.
Finally, one of the second hundred—a three-man ship, the minimum possible crew—managed to return. It was infected, with only one of the crew left alive.
All the other ships, they realized then, had also been infected. The crews had either destroyed themselves or had been caught in the Trap and forced out of the system into the permanent "quarantine" areas.
A series of cyborg ships was the solution Kremastor's contemporaries devised. Because the brain controlled the ship's functions directly through the computer, a single person—a single brain—could pilot the ship. Because the computer was programmed not to allow the pilot to shut himself down or damage himself in any way, he could not kill himself if—when—he became infected.
Because they expected the pilot to become infected and be forced out of the system by the Trap, they designed and built the nullifier, a device that could temporarily shut down the Trap. They could only hope that if he did indeed become infected, he would retain enough sanity to use the nullifier and complete his mission.
But Kremastor never got the chance, and he could only assume that those who had gone before had suffered similar fates.
He was infected virtually the instant he entered the system. Suddenly, he was terrified of everything, of the ship that was his own body, of the limbo that surrounded it, of his onetime friends and associates who had designed and built the ship and imprisoned him in it and sent him out, alone, to face an eternity of paralyzing terror.
And then the Trap reached out and grasped him and hurled him out of the system.
Despite the fact that his "body" was a mechanical and electronic thing, wired for neither pain nor pleasure, he experienced as much pain during the trapping as any fully organic victim ever had.
But the pain, he quickly realized, had been his salvation. In some way, it had overloaded the circuits of his brain so that when the pain stopped, the fear that remained was somehow tolerable. It still took a tremendous mental effort to overcome it, to work in spite of it, but after the sensory overload of the trapping, he was able to do it.
But he was not able to reenter the system. The nullifier, he discovered, would not work, nor would half the systems on his ship. His sensors and transporter worked only marginally, and no adjustment he was capable of making helped. If he had possessed a real body, he always thought, he might have been able to take the systems apart, find out why they didn't work, then rebuild and repair them. But working only from the inside, it was as impossible as a human performing open-heart surgery on himself.
So he had done what he could.
He had used his ailing sensors to learn what little he could from the hundreds of other ships that had apparently been trapped there before him. More than a hundred, he found, were those of either his contemporaries or his ancestors. Many of those who had gone ahead of him to attempt to shut down the system were here, all long dead, and now he had joined them.
Unable to shut himself down or even to sleep, he waited, hoping another ship, with a more effective nullifier, would come, not to save him but to complete the mission he himself had failed at.
But none came, and he soon began to wonder if, despite all the safeguards, his civilization had once again been destroyed by the creatures.
Finally, another ship had come through, but he did not recognize it. And when he tried to use his sensors on it, he discovered the dead space for the first time. It had blocked his sensors entirely, but it had shrunk and vanished in minutes, and when he was able to probe the ship, he found it crewed by aliens. Aliens who, not unexpectedly, had killed each other.
Over the millennia, then, more than a hundred additional alien ships had come. But all had been essentially the same.
Each one had only further confirmed his fears, reinforced his conviction that he was trapped here forever.
Until the Enterprise.
The moment the Enterprise dead space had touched him, the nullifier had revived. It had begun functioning, if not normally, close enough to normal to give him sudden hope that, after twenty thousand intolerable years, his mission might yet end in success.
But then, as they had been about to approach the nexus, the creature had begun to strengthen, and Kremastor's fear, until then under control, had broken free.
And, belatedly, the significance of the fact that the Enterprise crew, though infected, were still capable of working together dawned on him: they must be allied with the creature.
Perhaps they were even its creators.
And if they learned the secret of the nullifier from him, they could destroy the Trap, and they would be able once again to roam freely through the entire nexus system, infecting and destroying.
"But I could not simply run," Kremastor finished. iWhat if I were wrong? What if there were an innocent explanation for your survival? I tried to take your leader to question, but—"
"Time, Mr. Spock."
"Fourteen point seven minutes, Captain."
"Mr. Scott, are you finding anything of significance, either on the shuttlecraft or on Kremastor's ship?"
"Just what looks like the shortest route to cut through to reach Commander Ansfield, if it comes ta that. A complete check o' the shuttlecraft shows no change whatsoever because o' its wee trip."
"All right, Scotty, leave some people there, but you get back up to the engineering deck. I want you there, where you can keep an eye on the situation firsthand, when—if—that dead space closes in."
"Aye, Captain."
Cutting off the intercom, Kirk turned to Spock. "I won't make it an order, Spock, but your Vulcan abilities may be the only chance we have to communicate with this entity. If you still feel it is not hostile—"
"Of course, Captain. If nothing else, I can perhaps persuade it to leave us. Lieutenant Denslow, take the science station."
Spock was silent then for a brief moment as he stepped back. His features were still impassive, but Kirk sensed unease behind the surface. Then Spock strode past Uhura and the turbolift to the unmanned environmental station. There he lowered himself onto that station's chair. Stiffly, he placed his hands on his knees, palms down.
"Captain," he said in a voice that was quiet even for him. "I strongly recommend that you keep a phaser, set to heavy stun, trained on me at all times." Without further comment, he extended his arms directly in front of himself, lifted his head slightly, and closed his eyes.
"Dr. McCoy," Kirk said into the intercom, "to the bridge. We're about to hold a seance, and I think we should have a doctor in attendance."