"I've got to go. But I'll be back as fast as I can. It's a promise, Raissta! A promise!"

Siferra paused only long enough to snatch a pick and a brush from the equipment tent, which had been knocked askew by the sandstorm but was still reasonably intact. Then she went scrambling up the side of the Hill of Thombo, with Balik ponderously hauling himself right behind her. Young Eilis 18 had appeared from the shelter by the cliff now, and he stood below, staring up at them. Thuvvik and his corps of workmen were a little farther back, watching, scratching their heads in puzzlement.

"Watch out," Siferra called to Balik, when she had reached the beginning of the open gouge in the hill that the sandstorm had carved. "I'm going to run a trial cut."

"Shouldn't we photograph it first, and-"

"I told you to watch out," she said sharply, as she dug her pick into the hillside and sent a shower of loose soil tumbling down onto his head and shoulders.

He jumped aside, spitting out sand.

"Sorry," she said, without looking down. She cut into the hillside a second time, widening the storm gouge. It wasn't the best of technique, she knew, to be slashing away like this. Her mentor, grand old Shelbik, was probably whirling in his grave. And the founder of their science, the revered Galdo 221, no doubt was looking down from his exalted place in the pantheon of archaeologists and shaking his head sadly.

On the other hand, Shelbik and Galdo had had chances of their own to uncover whatever lay in the Hill of Thombo, and they hadn't done it. If she was a little too excited now, a little too hasty in her attack, well, they would simply have to forgive her. Now that the seeming calamity of the sandstorm had been transformed into serendipitous good fortune, now that the apparent ruination of her career had turned unexpectedly into the making of it, Siferra could not hold herself back from finding out what was builed here. Could not. Absolutely could not.

"Look-" she muttered, knocking a great mass of overburden away and going to work with her brush. "We've got a charred layer here, right at the foundation level of the cyclopean city. The place must have burned clear down to the stone. But you look a little lower on the hill and you can see that the crosshatch-style town is sitting right under the fire line-the cyclopean people simply plunked this whole monumental foundation down on top of the older city-"

"Siferra-" said Balik uneasily.

"I know, I know. But let me at least begin to see what's here. Just a quick probe now, and then we can go back to doing things the proper way." She felt as though she were perspiring from head to toe. Her eyes were starting to ache, so fiercely was she staring. "Look, will you? We're way up on top of the hill, and we've already got two towns. And it's my guess that if we unzip the mound a little further, someplace around where we'd expect to find the foundations of the crosshatch people, we'll- yes! Yes! There! By Darkness, will you look at that, Balik! Just look!"

She pointed triumphantly with the tip of her pick.

Another dark line of charcoal was apparent, near the foundations of the crosshatch-style building. The second highest level had also been destroyed by fire just as the cyclopean one had. And from the way things looked, it was sitting atop the ruins of an even older village. Balik now had caught her fervor too. Together they worked to lay bare the outer face of the hill, midway between ground level and the shattered summit. Eilis called up to them to ask what on Kalgash they were doing, but they ignored him. Aflame with eagerness and curiosity, they cut swiftly through the ancient packing of windblown sand, moving three inches farther down the hill, six, eight- "Do you see what I see?" Siferra cried, after a time.

"Another village, yes. But what kind of style of architecture is that, would you say?"

She shrugged. "It's a new one on me."

"And me too. Something very archaic, that's for sure."

"No question of it. But I think it's not the most archaic thing we've got here, not by plenty." Siferra peered down toward the distant ground. "You know what I think, Balik? We've got five towns here, six, seven, maybe eight, each one right on top of the next. You and I may spend the rest of our lives digging in this hill!"

They looked at each other in wonder.

"We'd better get down and take some photos now," he said quietly.

"Yes. Yes, we'd better do that." She felt almost calm, suddenly. Enough of this furious hacking and slashing, she thought. It was time to go back to being a professional now. Time to approach this hill like a scholar, not a treasure-hunter or a journalist.

Let Balik take his photographs, first, from every side. Then take the soil samples at the surface level, and put in the first marker stakes, and go through all the rest of the standard preliminary procedures. -

Then a trial trench, a bold shaft right through the hill, to give us some idea of what we've really got here.

And then, she told herself, we'll peel this hill layer by layer. We'll take it apart, carving away each stratum to look at the one below it, until we're down to virgin soil. And by the time we're done with that, she vowed, we'll know more about the prehistory of Kalgash than all my predecessors put together have been able to learn since archaeologists first came here to Beklimot to dig.

Kelaritan said, "We've arranged everything for your inspection of the Tunnel of Mystery, Dr. Sheerin. If you'll be down in front of your hotel in about an hour, our car will pick you up."

"Right," Sheerin said. "See you in about an hour."

The plump psychologist put down the phone and stared solemnly at himself in the mirror opposite his bed.

The face that looked back at him was a troubled one. He seemed so wasted and haggard that he tugged at his cheeks to assure himself that they were still there. Yes, there they were, his familiar fleshy cheeks. He hadn't lost an ounce. The haggardness was all in his mind.

Sheerin had slept badly-had scarcely slept at all, so it seemed to him now-and yesterday he had only picked at his food. Nor did he feel in the least hungry now. The thought of going downstairs for breakfast had no appeal whatever. That was an alien concept to him, not to feel hungry.

Was the bleakness of his mood, he wondered, the result of his interviews with Kelaritan's hapless patients yesterday?

Or was he simply terrified of going through the Tunnel of Mystery?

Certainly seeing those three patients hadn't been easy. It was a long time since he'd done any actual clinical work, and obviously his sojourn among the academics at Saro University had attenuated the professional detachment that allows members of the healing arts to confront the ill without being overwhelmed by compassion and sorrow. Sheerin was surprised at that, how tenderhearted he seemed to have become, how thin-skinned.

That first one, Harrim, the longshoreman-he looked tough enough to withstand anything. And yet fifteen minutes of Darkness on his trip through the Tunnel of Mystery had reduced him to such a state that merely to relive the trauma in memory sent him into babbling hysteria. How terribly sad that was.

And then the other two, in the afternoon-they had been in even worse shape. Gistin 190, the schoolteacher, that lovely frail woman with the dark, intelligent eyes-she hadn't been able to stop sobbing for a moment, and though she was able to speak clearly and well, at least in the beginning, her story had degenerated into mere incoherent blurtings within a few sentences. And Chimmilit 97, the high school athlete, obviously a perfect physical specimen-Sheerin wasn't going quickly to forget how the boy had reacted to the sight of the afternoon sky when Sheerin opened the blinds in his room. There was Onos blazing away in the west, and all that huge handsome boy could manage to say was, "The Darkness-the Darkness-" before he turned away and tried to scuttle down under his bed!

The Darkness-the Darkness- And now, Sheerin thought gloomily, it's my turn to take a ride in the Tunnel of Mystery.

Of course, he could simply refuse. There was nothing in his consulting contract with the Municipality of Jonglor that required him to risk his sanity. He'd be able to render a valid enough opinion without actually sticking his neck into peril.

But something in him rebelled at such timidity. His professional pride, if nothing else, was pushing him toward the Tunnel He was here to study the phenomenon of darkness and to help these people work out ways not only of healing the present victims but of preventing recurrences of these tragedies. How could he deign to explain what had happened to the Tunnel's victims if he didn't make a close study of the cause of their disturbances? He bad to. It would be sheer malfeasance to back out.

Nor did he want anyone, not even these strangers here in Jonglor, to be able to accuse him of cowardice. He remembered the taunts of his childhood: "Fatty is a coward! Fatty is a coward!" All because he hadn't wanted to climb a tree that was obviously beyond the capabilities of his heavy, ill-coordinated body.

But Fatty wasn't a coward. Sheerin knew that. He was content with himself: a sane, well-balanced man. He simply didn't want other people making incorrect assumptions about him because of his unheroic appearance.

Besides, fewer than one out of ten of those who had gone through the Tunnel of Mystery had come out of it showing any symptoms of emotional disturbance. And those people must have been vulnerable in some special way. Precisely because he was so sane, Sheerin told himself, because he was so well balanced, he had nothing to fear.

Nothing- Th- Fear- He kept repeating those words to himself until he felt almost calm.

Even so, Sheerin was something other than his customary jolly self as he went downstairs to wait for the hospital car to pick him up.

Kelaritan was there, and Cubello, and a striking-looking woman named Varitta 312, who was introduced to him as one of the engineers who had designed the Tunnel. Sheerin greeted them all with hearty handshakes and a broad smile that he hoped seemed convincing.

"A nice day for a trip to the amusement park," he said, trying to sound jovial.

Kelaritan looked at him oddly. "I'm glad you feel that way. Did you sleep well, Dr. Sheerin?"

"Very well, thanks. As well as could be expected, I should say. After seeing those unhappy people yesterday."

Cubello said, "You aren't optimistic about their chances of recovery, then?"

"I'd like to be," Sheerin told the lawyer ambiguously.

The car moved smoothly down the street.

"It's about a twenty-minute drive to the Centennial Exposition grounds," Kelaritan said. "The Exposition itself will be crowded-it is every day-but we've had a big section of the amusement area roped off so that we won't be disturbed. The Tunnel of Mystery itself, as you know, has been shut down since the full extent of the troubles became apparent."

"You mean the deaths?"

"Obviously we couldn't allow the ride to remain open after that," Cubello said. "But you must realize that we were considering shutting down much earlier. It was a question of determining whether the people who appeared to have been disturbed by their trips through the Tunnel were actually suffering harm or were merely falling in with popular hysteria."

"Of course," Sheerin said, his tone a dry one. "The City Council wouldn't have wanted to close down such a profitable attraction except for a really good reason. Such as having a bunch of the customers drop dead from fright, I suppose."

The atmosphere in the car became exceedingly chilly.

Kelaritan said, after a time, "The Tunnel was not only a profitable attraction but also one that nearly everyone who attended the Exposition was eager to experience, Dr. Sheerin. I understand that thousands of people had to be turned away every day."

"Even though it was obvious from the very first day that some of those who rode through the Tunnel, like Harrim and his family, were coming out of it in psychotic states?"

"Especially because of that, Doctor," Cubello said.

"What?"

"Forgive me if I seem to be explaining your own specialty to you," the lawyer said unctuously. "But I'd like to remind you that there's a fascination in being frightened when it ~c part of a game. A baby is born with three instinctive fears: of loud noises, of falling, and of the total absence of light. That's why it's considered so funny to jump at someone and shout 'Boo!' That's why it's such fun to ride a roller coaster. And that's why the Tunnel of Mystery was something everybody wanted to see at first hand. People came out of that Darkness shaking, breathless, half dead with fear, but they kept on paying to get in. The fact that a few of those who took the ride came out of it in a rather intense state of shock only added to the appeal."

"Because most people assumed that they 'd be tough enough to withstand whatever it was that had shaken up the others so much, is that it?"

"Exactly, Doctor."

"And when some people came out not just highly upset but actually dead of fright? Even if the Exposition managers couldn't see their way clear to shutting the thing down after that, I'd imagine that potential customers would have become few and far between, once the news of the deaths got around."

"Ah, quite the contrary," said Cubello, smiling triumphantly. "The same psychological mechanism operated, though even more strongly. After all, if people with weak hearts wanted to go through the Tunnel, it was at their own risk- why be surprised at what happened to them? The City Council discussed the whole thing at great length and agreed finally to put a doctor in the front office and have every customer undergo a physical examination before getting into the car. That actually boosted ticket sales."

"In that case," Sheerin said, "why is the Tunnel shut down now? From what you've told me, I'd expect it to be doing terrific business, lines stretching from Jonglor all the way to Khunabar, mobs of people going in the front way and a steady stream of corpses being hauled out the back."

"Dr. Sheerin!"

"Well, why isn 't it still open, if even the deaths didn't trouble anybody?"

"The liability insurance problem," Cubello said.

"Ah. Of course."

"Despite your grisly little turn of phrase just now, actual deaths were very few and far between-three, I think, or maybe five. The families of those who passed away were given adequate indemnities and the cases were closed. What ultimately became a problem for us was not the death rate but the survival rate among those who underwent traumatic disturbance. It began to become clear that some might require hospitalization for prolonged periods-an ongoing expense, a constant financial drain on the municipality and its insurers."

"I see," Sheerin said morosely. "If they simply fall down dead, it's a one-shot cost. Buy off the relatives and that's that. But if they linger for months or years in a public institution, the price can get to be too high."

"Perhaps a little harshly put," said Cubello. "But that is essentially the calculation the City Council was forced to make."

"Dr. Sheerin seems a little testy this morning," Kelaritan said to the lawyer. "Possibly the idea of going through the Tunnel himself is troublesome to him."

"Absolutely not," said Sheerin at once.

"Of course you understand that there is no real necessity for you to-"

"There is," Sheerin said.

There was silence in the car. Sheerin peered somberly at the changing landscape, the curious angular scaly-barked trees, the bushes with flowers of odd metallic hues, the peculiarly high and narrow houses with pointed eaves. He had rarely been this far north before. There was something very disagreeable about the look of the entire province-and about this crew of mealymouthed cynical people, too. He told himself that he'd be glad to get home to Saro again.

But first-the Tunnel of Mystery- The Jonglor Centennial Exposition was spread over a vast area of parkland just east of the city. It was a mini-city in itself, and quite spectacular in its own way, Sheerin thought. He saw fountains, arcades, shining pink and turquoise towers of iridescent stone-hard plastic. Great exhibit halls offered art treasures from every province of Kalgash, industrial displays, the latest scientific marvels. Wherever he looked there was something unusual and beautiful to engage his eye. Thousands of people, perhaps hundreds of thousands, strolled its glittering, elegant boulevards and avenues.

Sheerin had always heard that the Jonglor Centennial Exposition was one of the marvels of the world, and he saw now that it was true. To be able to visit it was a rare privilege. It was open only once every hundred years, for a three-year run, to commemorate the anniversary of the city's founding-and this, Jonglor's Fifth Centennial Exposition, was said to be the greatest of all. Indeed he felt sudden buoyant excitement, such as he had not known in a long while, as he traveled through its wellmanicured grounds. He hoped that he'd have some time later in the week to explore it on his own.

But his mood changed abruptly as the car swung around the perimeter of the Exposition and brought them to an entrance in back that led to the amusement area. Here, just as Kelaritan had said, great sections were roped off; and sullen crowds peered across the ropes in obvious annoyance as Cubello, Kelaritan, and Varitta 312 led him toward the Tunnel of Mystery. Sheerin could hear them muttering angrily, a low harsh growling that he found unsettling and even a little intimidating.

He realized that the lawyer had told the truth: these people were angry because the Tunnel was closed.

They're jealous, Sheerin thought in wonder. They know we're going to the Tunnel, and they want to go too. Despite everything that's happened there.

"We can go in this way," Varitta said.

The facade of the Tunnel was an enormous pyramidal structure, tapering away at the sides in an eerie, dizzying perspective. In the center of it was a huge six-sided entrance gate, dramatically outlined in scarlet and gold. Bars had been drawn across it. Varitta produced a key and unlocked a small door to the left of the facade, and they stepped through.

Inside, everything seemed much more ordinary. Sheerin saw a series of metal railings no doubt designed to contain the lines of people waiting to board the ride. Beyond that was a platform much like that in any railway station, with a string of small open cars waiting there. And beyond that- Darkness.

Cubello said, "If you don't mind signing this first, please, Doctor-"

Sheerin stared at the paper the lawyer had handed him. It was full of words, blurred, dancing about.

"What is this?"

"A release. The standard form."

"Yes. Of course." Airily Sheerin scrawled his name without even trying to read the paper.

You are not afraid, he told himself. You fear nothing at all.

Varitta 312 put a small device in his hand. "An abort switch," she explained. "The full ride lasts fifteen minutes, but you just have to press this green panel here as soon as you've been inside long enough to have learned what you need to know-or in case you begin to feel uncomfortable-and lights will come on. Your car will go quickly to the far end of the Tunnel and circle back to the station."

"Thank you," Sheerin said. "I doubt that I'll need it."

"But you should have it. Just in case."

"It's my plan to experience the ride to the fullest," he told her, enjoying his own pomposity.

But there was such a thing as foolhardiness, he reminded himself. He didn't intend to use the abort switch, but it was probably unwise not to take it.

Just in case.

He stepped out on the platform. Kelaritan and Cubello were looking at him in an all too transparent way. He could practically hear them thinking, This fat old fool is going to turn to jelly in there. Well, let them think it.

Varitta had disappeared. No doubt she had gone to turn on the Tunnel mechanism.

Yes: there she was now, in a control booth high up to the right, signaling that everything was ready.

"If you'll board the car, Doctor-" Kelaritan said.

"Of course. Of course."

Fewer than one out of ten experienced harmful effects. Very likely they were unusually vulnerable to Darkness disorders to begin with. I am not. I am a very stable individual.

He entered the car. There was a safety belt; he strapped it around his waist, adjusting it with some difficulty to his girth. The car began to roll forward, slowly, very slowly.

Darkness was waiting for him.

Fewer than one out often. Fewer than one out of ten.

He understood the Darkness syndrome. That would protect him, he was sure: his understanding. Even though all of mankind had an instinctive fear of the absence of light, that did not mean that the absence of light was of itself harmful.

What was harmful, Sheerin knew, was one's reaction to the absence of light. The thing to do is to stay calm. Darkness is nothing but darkness, a change of external circumstances. We are conditioned to abhor it because we live in a world where darkness is unnatural, where there is always light, the light of the many suns. At any time there might be as many as four suns shining at once; usually there were three in the sky, and at no time were there ever less than two-and the light of any of them was sufficient all by itself to hold back the Darkness.

The Darkness- The Darkness- The Darkness!

Sheerin was in the Tunnel now. Behind him the last vestige of light disappeared, and he peered into an utter void. There was nothing ahead of him: nothing. A pit. An abyss. A zone of total lightlessness. And he was tumbling headlong into it.

He felt sweat breaking out all over him.

His knees began to shake. His forehead throbbed. He held up his hand and was unable to see it in front of his face.

Abort abort abort abort

No. Absolutely not.

He sat upright, back rigid, eyes wide open, gazing stolidly into the nothingness through which he plunged. On and on, ever deeper. Primordial fears bubbled and hissed in the depths of his soul, and he forced them back down and away.

The suns are still shining outside the Tunnel, he told himself.

This is only temporary. In fourteen minutes and thirty seconds I'll be back out there.

Fourteen minutes and twenty seconds.

Fourteen minutes and ten seconds.