The rain was a slantwise curtain across the dingy street, washing soot from city walls, the taste of it metallic on the lips of the tall, thin man who walked with a loping stride close to the buildings, watching the mouths of doorways, the gaps of alleys with a narrow-eyed intentness.

Simon Tregarth had left the railroad station two -- or was it three hours ago? He had no reason to mark the passing of time any longer. It had ceased to have any meaning, and he had no destination. As the hunted, the runner, the hider -- no, he was not in hiding. He walked in the open, alert, ready, his shoulders as straight, his head as erect as ever.

In those first frantic days when he had retained a wisp of hope, when he had used every scrap of animal cunning, every trick and dodge he had learned, when he had twisted and back-trailed, and befogged his tracks, then he had been governed by hours and minutes, he had run. Now he walked, and he would continue to walk until the death lurking in one of those doorways, in ambush in some alley would confront him. And even then he would go down using his fangs. His right hand, thrust deep into the soggy pocket of his top coat, caressed those fangs -- smooth, sleek, deadly, a weapon which fitted as neatly into his palm as if it were a part of his finely trained body.

Tawdry red-and-yellow neon lights made wavering patterns across the water-slick pavement; his acquaintance with this town was centered about a hotel or two located at its center section, a handful of restaurants, some stores, all that a casual traveler learned in two visits half a dozen years apart. And he was driven by the urge to remain in the open, for he was convinced that the end to the chase would come that night or early tomorrow.

Simon realized that he was tiring. No sleep, the need for constant sentry go. He slackened pace before a lighted doorway, read the legend on the rain-limp awning above it. A doorman swung open the inner portal and the man in the rain accepted that tacit invitation, stepping into warmth and the fragrance of food.

The bad weather must have discouraged patrons. Maybe that was why the headwaiter welcomed him so quickly. Or perhaps the cut of the still presentable suit protected from the damp by the coat he shed, his faint but unmistakable natural arrogance -- the mark left upon a man who has commanded his kind and been readily obeyed -- insured for him the well-placed table and the speedily attentive waiter.

Simon grinned wryly as his eye sped down the lines of the menu, and there was a ghost of true humor in that grin. The condemned man would eat a hearty meal anyway. His reflection, distorted by the curving side of the polished sugar bowl, smiled back at him. A long face, fine-drawn, with lines at the corners of the eyes, and deeper-set brackets at the lips, a brown face, well weathered, but in its way an ageless face. It had looked much the same at twenty-five, it would continue to look so at sixty.

Tregarth ate slowly, savoring each bite, letting the comforting warmth of the room, of the carefully chosen wine, relax his body if not mind and nerves. But that relaxation nurtured no false courage. This was the end, he knew it -- had come to accept it.

"Pardon..."

The fork he had raised with its thick bite of steak impaled did not pause before his lips. But in spite of Simon's iron control a muscle twitched in his lower eyelid. He chewed, and then he answered, his voice even.

"Yes?"

The man standing politely at his table might be a broker, a corporation lawyer, a doctor. He had a professional air designed to inspire confidence in his fellows. But he was not what Simon had expected at all, he was too respectable, too polite and correct to be -- death! Though the organization had many servants in widely separated fields.

"Colonel Simon Tregarth, I believe?"

Simon broke a muffin apart and buttered it. "Simon Tregarth, but not 'Colonel,'" he corrected, and then added with a counterthrust on his own, "As you well know."

The other seemed a little surprised, and then he smiled, that smooth, soothing, professional smile.

"How maladroit of me, Tregarth. But let me say at once -- I am not a member of the organization. I am, instead -- if you wish it, of course -- a friend of yours. Permit me to introduce myself. I am Dr. Jorge Petronius. Very much at your service, may I add."

Simon blinked. He had thought the scrap of future remaining to him well accounted for, but he had not reckoned on this meeting. For the first time in bitter days he felt, far inside him, the stir of something remotely akin to hope.

It did not occur to him to doubt the identification offered by this small man watching him narrowly now through the curiously thick lenses, supported by such heavy and broad black plastic frames that Petronius appeared to wear the half-mask of eighteenth-century disguise. Dr. Jorge Petronius was very well known throughout that half-world where Tregarth had lived for several violent years. If you were "hot" and you were also lucky enough to be in funds you went to Petronius. Those who did were never found thereafter, either by the law, or the vengeance of their fellows.

"Sammy is in town," that precise, slightly accented voice continued.

Simon sipped appreciatively at his wine. "Sammy?" he matched the other's detachment. "I am flattered."

"Oh, you have something of a reputation, Tregarth. For you the organization unleashed their best hounds. But after the efficient way you dealt with Kotchev and Lampson, there remained only Sammy. However, he is slightly different metal from the others. And you have, if you will forgive my prying into your personal affairs, been on the run for some time. A situation which does not exactly strengthen the sword arm."

Simon laughed. He was enjoying this, the good food and drink, even the sly needling of Dr. Jorge Petronius. But he did not lower his guard.

"So, my sword arm needs strengthening? Well, Doctor, what do you suggest as the remedy?"

"There is -- my own."

Simon put down his wineglass. A red drop trickled down its side to be absorbed by the cloth.

"I have been told your services come high, Petronius."

The small man shrugged. "Naturally. But in return I can promise complete escape. Those who trust me receive the worth of their dollars. I have had no complaints."

"Unfortunately I am not one who can afford your services."

"Your recent activities having so eaten into your cash reserve? But, of course. However, you left San Pedro with twenty thousand. You could not have completely exhausted such a sum in this short interval. And if you meet Sammy what remains shall only be returned to Hanson."

Simon's lips tightened. For an instant he looked as dangerous as he was, as Sammy would see him if they had a fair, face-to-face meeting.

"Why hunt me up -- and how?" he asked.

"Why?" Again Petronius shrugged. "That you shall understand later. I am, in my way, a scientist, an explorer, an experimenter. As for how I knew you were in town and in need of my service -- Tregarth, you should be aware by now how rumor spreads. You are a marked man and a dangerous one. Your coming and going is noted. It is a pity for your sake that you are honest."

Simon's right hand balled into a fist. "After my activities of the past seven years you apply that label to me?"

It was Petronius who laughed now, a small chuckle, inviting the other to enjoy the humor of the situation. "But honesty sometimes has very little to do with the pronouncements of the law, Tregarth. If you had not been an essentially honest man -- as well as one with ideals -- you would never have stood up to Hanson. It is because you are what you are that I know you are ripe for me. Shall we go?"

Somehow Simon found himself paying his check, following Dr. Jorge Petronius. A car waited at the curb, but the doctor did not address its driver as the machine carried them into the night and the rain.

"Simon Tregarth." Petronius' voice was as impersonal now as if he recited data important only to himself. "Of Cornish descent. Enlisted in the U.S. Army on March tenth, 1939. Promoted on the field from sergeant to lieutenant, and climbed to rank of lieutenant colonel. Served in the occupation forces until stripped of his commission and imprisoned for -- for what, Colonel? Ah, yes, for flagrant black market dealing. Only, most unfortunately the brave colonel did not know he had been drawn into a criminal deal until too late. That was the point, was it not, Tregarth, which put you on the other side of the law? Since you had been given the name you thought you might as well play the game.

"Since Berlin you have been busy in quite a few dubious exploits, until you were unwise enough to cross Hanson. Another affair into which you were pushed unknowingly? You seem to be an unlucky man, Tregarth. Let us hope that your fortunes change tonight."

"Where are we going -- to the docks?"

Again he heard that rich chuckle. "We head downtown, but not to the harbor. My clients travel, but not by sea, air, or land. How much do you know of the traditions of your fatherland, Colonel?"

"Matacham, Pennsylvania, has no traditions I ever heard of--"

"I am not concerned with a crude mining town on this continent. I am speaking of Cornwall, which is older than time -- our time."

"My grandparents were Cornish. But I don't know any more than that." "Your family was of the pure blood, and Cornwall is old, so very old. It is associated with Wales in legends. Arthur was known there, and the Romans of Britain huddled within its borders when the axes of the Saxons swept them to limbo. Before the Romans there were others, many, many others, some of them bearing with them scraps of strange knowledge. You are going to make me very happy, Tregarth." There was a pause as if inviting comment; when Simon did not answer, the other continued.

"I am about to introduce you to one of your native traditions, Colonel. A most interesting experiment. Ah, here we are!"

The car had stopped before the mouth of a dark alley. Petronius opened the door.

"You now behold the single drawback of my establishment, Tregarth. This lane is too narrow to accommodate the car; we must walk."

For a moment Simon stared up the black mouth, wondering if the doctor had brought him to some appointed slaughterhouse. Did Sammy wait here? But Petronius had snapped on a torch and was waving its beam ahead in invitation.

"Only a yard or two, I assure you. Just follow me."

The alley was indeed a short one and they came out into an empty space between towering buildings. Squatting in a hollow ringed about by these giants was a small house.

"You see here an anachronism, Tregarth." The doctor set a key in the door lock. "This is a late seventeenth-century farmhouse in the heart of a twentieth-century city. Because its title is in doubt, it exists, a very substantial ghost of the past to haunt the present. Enter, please."

Later, as he steamed in front of an open fire, a mixture his host had pressed upon him in his hand, Simon thought that Petronius' description of a ghost house was very apt. It needed only a steeple-crowned hat for the doctor's head, a sword at his own side, to complete the illusion that he had stepped from one era into another.

"Where do I go from here?" he asked.

Petronius prodded the fire with a poker. "You shall go at dawn, Colonel, free and clear, as I promise. As to where," he smiled, "that we shall see."

"Why wait until dawn?"

As if being forced into telling more than he wished, Petronius put down the poker and wiped his hands on a handkerchief before he faced his client squarely.

"Because only at dawn does your door open -- the proper one for you. This is a story at which you may scoff, Tregarth, until you see the proof before your eyes. What do you know of menhirs?"

Simon felt absurdly pleased that he could supply an answer the other obviously did not expect.

"They were stones -- set in circles by prehistoric men -- Stonehenge."

"Set up in circles, sometimes. But they had other uses also." Petronius was all unsuppressed eagerness now, begging for serious attention from his listener. "There were certain stones of great power mentioned in the old legends. The Lia Fail of the Tuatha De Danann of Ireland. When the rightful king trod upon it, it shouted aloud in his honor. It was the coronation stone of that race, one of their three great treasures. And do not the kings of England to this day still cherish the Stone of Scone beneath their throne?

"But in Cornwall there was another stone of power -- the Siege Perilous. It was one rumored to be able to judge a man, determine his worth, and then deliver him to his fate. Arthur was supposed to have discovered its power through the Seer Merlin and incorporated it among the seats of the Round Table. Six of his knights tried it -- and disappeared. Then came two who knew its secret and stayed: Percival and Galahad."

"Look here." Simon was bitterly disappointed, the more so because he had almost dared to hope again. Petronius was cracked, there was no escape after all. "Arthur and the Round Table -- that's a fairy tale for kids. You're talking as if--"

"As if it were true history?" Petronius caught him up. "Ah, but who is to say what is history and what is not? Every word of the past which comes to us is colored and influenced by the learning, the prejudices, even the physical condition of the historian who has recorded it for later generations. Tradition fathers history and what is tradition but word of mouth? How distorted may such accounts become in a single generation? You yourself had your entire life changed by perjured testimony. Yet that testimony has been inserted in records, has now become history, untrue as it is. How can anyone say that this story is legend but that one a fact, and know that he is correct? History is made, is recorded by human beings, and it is larded with all the errors our species is subject to. There are scraps of truth in legend and many lies in accepted history. I know -- for the Siege Perilous does exist!

"There are also theories of history alien to the conventional ones we learn as children. Have you ever heard of the alternate worlds which may stem from momentous decisions? In one of those worlds, Colonel Tregarth, perhaps you did not turn aside your eyes on that night in Berlin. In another you did not meet with me an hour ago, but went on to keep your rendezvous with Sammy!"

The doctor rocked back and forth on his heels, as if set teetering by the force of his words and belief. And in spite of himself Simon caught a bit of that fiery enthusiasm.

"Which of these theories do you intend to apply to my problem?"

Petronius laughed, once again at ease. "Just have the patience to hear me out without believing that you are listening to a madman, and I shall explain." He glanced from the watch on his wrist to the wall clock behind him. "We have some hours yet. So, it is like this--"

As the little man began mouthing what sounded like wild nonsense, Simon obediently listened. The warmth, the drink, the chance to rest were payment enough. He might have to leave to face Sammy later, but that chance he pushed to the back of his mind as he concentrated on what Petronius was saying.

The mellow chime of the ancient clock struck the hour three times before the doctor was done. Tregarth sighed, perhaps he had only been battered into submission by that flood of words, but if it were true -- And there was Petronius' reputation. Simon unbuttoned his shirt and drew out his money belt.

"I know that Sacarsi and Wolverstein haven't been heard of since they contacted you," he conceded.

"No, for they went through their doors; they found the worlds they had always unconsciously sought. It is as I have told you. One takes his seat upon the Siege and before him opens that existence in which his spirit, his mind -- his soul if you wish to call it that -- is at home. And he goes forth to seek his fortune there."

"Why haven't you tried it yourself?" That was to Simon the weak point in the other's story. If Petronius possessed the key to such a door, why had he not used it himself?

"Why?" The doctor stared down at the two plump hands resting on his knees. "Because there is no return -- and only a desperate man chooses an irrevocable future. In this world we always cling to the belief that we can control our lives, make our own decisions. But through there, we have made a choice which cannot be canceled. I use words, many words, but at this moment I cannot seem to choose them rightly to express what I feel. There have been many Guardians of the Siege -- only a few of them have used it for themselves. Perhaps... someday... but as yet I have not the courage."

"So you sell your services to the hunted? Well, that is one way of making a living. A list of your clients might make interesting reading."

"Correct! I have had some very famous men apply for assistance. Especially at the close of the war. You might not believe the identity of some who sought me out then, after fortune's wheel spun against them."

Simon nodded. "There were some notable gaps in the war criminal captures," he remarked. "And some odd worlds your stone must have opened if your tale is true." He arose and stretched. Then went to the table and counted out the money he took from his belt. Old bills, most of them, dirty, with a greasy film as if the business they had been used for had translated some of its slime to their creased surfaces. There remained in his hand a single coin. Simon spun it in the air and let it ring down on the polished wood. The engraved eagle lay up. He looked at it for a moment and then picked it up again.

"This I take."

"A luck piece?" The doctor was busy with the bills, stacking them into a tidy pile. "By all means retain it, then; a man can never have too much luck. And now, I dislike speeding the parting guest, but the power of the Siege is limited. And the proper moment is all-important. This way, please."

He might have been ushering one into a dentist's office, or to a board meeting, Simon thought. And perhaps he was a fool to follow.

The rain had stopped, but it was still dark in the square box of yard behind the old house. Petronius pushed a switch and a light fanned out from the back door. Three gray stones formed an arch which topped Simon's head by a few scant inches. And before that lay a fourth stone, as unpolished, unshaped and angular as the others. Beyond that arch was a wooden fence, high, unpainted, rotted with age, grimed with city dirt, and a foot or two of sour slum soil, nothing else.

Simon stood for a long moment, inwardly sneering at his half-belief of a few moments earlier. Now was the time for Sammy to appear and Petronius to earn his real fee.

But the doctor had taken his stand to one side of the clock on the ground. He indicated it with a forefinger.

"The Siege Perilous. If you will just take your seat there, Colonel -- it is almost time."

A grin, without humor, to underline his own folly, twisted Simon's thin-lipped mouth, as he straddled the stone and then stood for an instant partly under that arch before he sat down. There was a rounded depression to fit his hips. Curiously, with a sense of foreboding, he put out his hands. Yes, there were two other, smaller hollows to hold his palms, as Petronius had promised.

Nothing happened. The wooden fence, the strip of musty earth remained. He was about to stand up when--

"Now!" Petronius' voice fluted in a word which was half call.

There was a swirling within the stone arch, a melting.

Simon looked out across a stretch of moorland which lay under a gray dawn sky. A fresh wind laden with a strange, invigorating scent fingered his hair. Something within him straightened like a leashed hound to trace that wind to its source, run across that moorland.

"Your world, Colonel, and I wish you the best of it!"

He nodded absently, no longer interested in the little man who called to him. This might be an illusion, but it drew him as nothing else ever had in his life. Without a word of farewell Simon arose and strode beneath the arch.

There was an instant of extreme panic -- such fear as he had never imagined could exist, worse than any physical pain -- as if the universe had been wrenched brutally apart and he had been spilled out into an awful nothingness. Then he sprawled facedown on thick wiry turf.