“We’ll soon take care of that,” the merchant promised.

  As if to bear him out, the road swung sharply around a stand of chedar trees and the city which they had been glimpsing sprang into full view. Massive, turreted, tawny, its walls reared above riverside docks. From within their seven-mile perimeter lifted the smoke of hearths and workshops, drifted the noise of wheels and hoofs, while traffic flowed in and out the great gates, walking, riding, driving. Settlements clustered close around a strip kept clear for defense: houses, inns, industries, gardens.

  Like the caravaneers, the dwellers were predominantly Iranian. Their ancestors founded the town, naming it Zariaspa, the City of the Horse. To the Greeks it was Bactra, and the nearer to it you came, the more Greeks you saw. Some of their kind had entered this country when the Persian Empire held it. Often that movement was involuntary, the Achaemenid shahs deporting troublesome Ionians. After Alexander took it, immigration increased, for Bactria had turned into a land of opportunity, which finally made itself an independent kingdom ruled by Hellenes. The large majority of them were in the cities, or in the military, or plying trade routes that reached west to the Mediterranean, south to India, east to China.

  Everard recalled hovels, medieval ruins, impoverished farmers and herders, mostly Turkic-Mongolian Uzbegs. But that was in Afghanistan, 1970, not far below the Soviet border. A lot of change and chance would blow from the steppes in the millennia to come. Too damn much.

  He clucked at his mount. Hipponicus’ had broken into a trot. The camel drivers made their own beasts shamble faster, and the men afoot happily kept pace. They were almost home.

  Home to war, Everard knew.

  They entered by the Scythian Gate. It stood open, but a squad of soldiers kept watch, helmets, shields, cuirasses, greaves, pikeheads ablaze in the sunlight. They turned a wary eye on everybody who passed. The bustle also seemed rather subdued, folk speaking less loudly and more curtly than was usual in the East. Pulled by oxen or donkeys, quite a few wooden carts were laden with family goods, the peasants who drove them accompanied by wives and children—seeking refuge behind the walls, if they could afford it.

  Hipponicus noticed. His mouth tightened. “Bad news has come,” he opined to Everard. “Only rumors, I’m sure, but truth hard on their heels. Hermes rates a sacrifice from me, that we arrived no later than now.”

  Yet everyday life went on. It always does, somehow, till the jaws close shut upon it. Between buildings generally blank-fronted but often vividly painted, people thronged the streets. Wagons, beasts of burden, porters, women balancing water jugs or market baskets on their heads, maneuvered among artisans, laborers, household slaves. A wealthy man in a litter, an officer on horseback, once a war elephant and its mahout, thrust straight through, leaving bow waves and wakes of human turbulence. Wheels groaned, hoofs clopped, sandals slapped cobblestones. Gabbling, laughter, anger, a snatch of song, a flute-lilt or drum-thump, roiled odors of sweat, dung, smoke, cookery, incense. In the shade of foodstalls, men sat cross-legged, sipping wine, playing board games, watching the world brawl past.

  Along the Sacred Way were a library, an odeon, a gymnasium, marble-faced, stately with pillars and friezes. At intervals rose those ithyphallic stone posts, topped by bearded heads, known as herms. Elsewhere, Everard knew, were schools, public baths, a stadium, a hippodrome, and a royal palace modeled on the one in Seleucid Antioch. This main thoroughfare boasted side-walks, elevated above manure and garbage, with stepping stones at the crossings. Thus far had the seeds of Greek civilization spread.

  Yet it mattered not that the Greeks identified Anaitis with Aphrodite Ourania and built her a fane in their own style. She remained an Asian goddess, her cult the largest; and west of Bactria the upstart kingdom of Parthia would presently create a new Persian Empire.

  The temple of Anaitis loomed beside the Stoa of Nicanor, principal marketplace in town. Booths crowded the square: silk, linens, woolens, wine, spices, sweetmeats, drugs, gems, brasswork, silverwork, goldwork, ironwork, talismans—With the sellers crying their wares and the shoppers haggling over prices mingled vendors, dancers, musicians, soothsayers, wizards, prostitutes, beggars, idlers—The faces, the many-hued and many-formed garments had come from China, India, Persia, Arabia, Syria, Anatolia, Europe, the wild highlands and the savage northern plains—

  To Everard the scene was eerily half-familiar. He had witnessed its like in a score of different lands, in as many different centuries. Each was unique, but a prehistorically ancient kinship vibrated in them all. He had never been here before. The Balkh of his own birthtime held scarcely a ghost of Hellenic Bactra. But he knew his way around. A subtle electronics had printed into his brain the map, the history, the chief languages, and information that was never chronicled but that Chandrakumar’s patience had gleaned.

  So much preparation, so long and risky an effort, to clap hands on four fugitives.

  They threatened his world’s existence.

  “This way!” yelled Hipponicus, gesturing from the saddle. His caravan struggled on, into a less crowded district, to stop at a warehouse. There a couple of hours went by while the goods were unloaded, inventoried, and stored. Hipponicus gave his men five drachmas apiece on account and instructions about the stabling and care of the animals. He would meet them tomorrow at the bank where he kept most of his money and pay them off. Right now, everybody wanted to go home, hear what had been happening, celebrate as merrily as that news would allow.

  Everard waited. He missed his pipe, and a cold beer would have been overwhelmingly welcome. But a Time Patrolman learned how to outlast tedium. He half observed what went on, half daydreamed. After a while, he noticed he was remembering an afternoon two thousand years and more beyond this moment.

  1987 A.D.

  Sunshine, soft air, and city murmur passed through an open window. Beyond it, Everard saw Palo Alto going about a holiday weekend. The apartment he sat in was a Stanford student’s, comfortably shabby furniture, cluttered desk, bookcase crowded with miscellany, a National Wildlife Federation poster thumbtacked to the opposite wall. No trace remained of last night’s violence. Wanda Tamberly had seen to the fine details of cleanup. She must not suspect anything amiss when she returned from her family outing—she, four months younger in lifespan than Wanda who sat here now, a space-time universe younger in knowledge.

  Everard looked out no oftener than habitual alertness compelled. He much preferred to keep his attention on the comely California blonde. Light glowed in her hair and on the blue bathrobe that matched her eyes. Even granted that she’d slept the clock around, she’d bounced back from her experience astoundingly fast. A girl, or a boy for that matter, who’d been kidnapped by one of Pizarro’s Conquistadores and rescued in a teeth-skinning maneuver would have had every excuse for spending the next few days stupefied. Wanda had shared a large steak in her kitchen while asking intelligent questions. Here in the living room, she was still at it.

  “How does time travel work, anyway? Impossible and absurd, I’ve read.”

  He nodded. “According to today’s physics and logic, that’s true. They’ll learn better in the future.”

  “All the same—Okay, I’m into biology, but I’ve had some physics courses and I try to keep up, sort of. Science News, Analog—” She smiled. “I’m being honest, you see. Scientific American, when the style doesn’t make me doze off. Real honest!” Her humor faded. It had been defensive, he guessed. The situation remained critical, perhaps desperate. “You jump onto something sort of like a Buck Rogers motorcycle without wheels, work the controls, rise in the air, hover, fly, then push another control and you’re instantly someplace else, anywhere, anywhen. Regardless of altitude differences or—Where does the energy come from? And the earth spins, it goes around the sun, the sun orbits through the galaxy. How about that?”

  He shrugged, with a smile of his own. “E pur si muove.”

  “Huh? Oh. Oh, yeah. What Galileo muttered, after they made him agree the earth sits still. ‘Nevertheless, it moves.’ Right?”

  “Right. I’m surprised a, uh, a person of your generation knows the story.”

  “I don’t only skindive and backpack for recreation, Mr. Everard.” He heard a tinge of resentment. “I take a book along.”

  “Sure. Sorry. Uh—”

  “Frankly, I’m a little surprised you’d know.”

  Sure, he thought, no matter how wild the circumstances, you couldn’t mistake what I am, a plain Mid-westerner who’s never quite gotten the mud off his boots.

  Her voice softened. “But of course you live history.” The honey-colored head shook. “I can’t yet get a handle on it. Time travel. It won’t come real for me, in spite of everything that’s happened. Too fabulous. Am I being slow on the uptake, Mr. Everard?”

  “I thought we were using first names.” The norm of this period in America. Which, damn it, is not so alien to me. I base myself in it. I belong here too. I’m not really old. Born sixty-three years ago. Run up a lot more lifespan than that, traipsing around through time. But biologically I’m in my thirties, he wanted to tell her and mustn’t. Antisenescence treatment, preventive medicine future to this century. We Patrol agents have our perks. We need them, to carry us through some of the things we see. He wrenched his mind into an attempt at lightness. “Actually, Galileo never said what I quoted, under his breath or aloud. It’s a myth.” The kind of myth humans live by, more than they do by facts.

  “Too bad.” She leaned back on the sofa and, in her turn, smiled again. “Manse. Okay, then, those timecycles or hoppers or whatever you call them, they are what they are, and if you tried to explain, scientists today wouldn’t understand.”

  “They’ve got a glimmering already. Non-inertial reference frames. Quantum gravity. Energy from the vacuum. Bell’s theorem was lately violated in the laboratory, wasn’t it? Or won’t that happen for another year or two? Stuff about wormholes in the continuum, Kerr metrics, Tipler machines—Not that I understand it myself. Physics was not my best subject at the Patrol Academy, by a long shot. It’ll be many thousands of years from now when the last discoveries are made and the first working space-time vehicle is built.”

  She frowned, concentrating. “And . . . expeditions begin. Scientific, historical, cultural—commercial, I suppose? Even military? I hope not that. But I can see where they’d soon need police, a Time Patrol, to help and advise and rescue and . . . keep travelers in line, so you don’t get robberies or swindles or”—she grimaced—“taking advantage of people in the past. They’d be helpless against knowledge and apparatus from the future, wouldn’t they?”

  “Not always. As you can testify.”

  She started, then uttered a shaky laugh. “Hoo boy, can I ever! Are there many guys in history as tough and smart as Luis Castelar?”

  “Enough. Our ancestors didn’t know everything we do, but they did know things we don’t, stuff we’ve forgotten or leave moldering in our libraries. And they averaged the same brains.” Everard sat forward in his chair. “Yes, mainly we in the Patrol are cops, doing the work you mentioned, plus conducting research of our own. You see, we can’t protect the pattern of events unless we know it well. That’s our basic job, protection. That’s the reason the Danellians founded our corps.”

  She lifted her brows. “Danellians?”

  “English version of their name in Temporal. Temporal’s our mutual language, artificial, developed to deal with the twists and turns of time travel. The Danellians—Some of them appeared, will appear, when chronokinesis was newly developed.”

  He paused. His words turned low and slow. “That must have been . . . awesome. I met one once, for a few minutes. Didn’t get over it for weeks. Of course, no doubt they can disguise themselves when they want to, go among us in the form of human beings, if they ever want to. I’m not sure they do. They’re what comes after us in evolution, a million or more years uptime. The way we come after apes. At least that’s what most us suppose. Nobody knows for certain.”

  Her eyes went large, staring past him. “How much could Australopithecus know for certain about us?” she whispered.

  “Yeah.” Everard forced prosiness back into his tone. “They appeared, and commanded the founding of the Patrol. Otherwise the world, theirs and everybody’s, was doomed. It would not simply be wrecked, it would never have existed. On purpose or by accident, time travelers would change the past so much that everything future-ward of them would be something else; and this would happen again and again till—I don’t know. Till complete chaos, or the extinction of the human race, or something like that brought a halt, and time travel had never occurred in the first place.”

  She had gone pale. “But that doesn’t make sense.”

  “By ordinary logic, it doesn’t. Think, though. If you go into the past, you’re as free an agent as you ever were. What mystical powers has it got to constrain your actions that the present doesn’t have? None. You, Wanda Tamberly, could kill your father before he married. Not that you’d want to. But suppose, innocently bumbling around in a year when your parents were young, you did something that kept them from ever meeting each other.”

  “Would I . . . stop existing?”

  “No. You’d still be there in that year. You’ve mentioned a sister, though. She would never be born.”

  “Then where would I have come from?” Impishness flickered: “Hardly from under a cabbage leaf!” and died away.

  “From nowhere. From nothing. Cause-and-effect doesn’t apply. It’s sort of like quantum mechanics, scaled up from the subatomic to the human level.”

  Almost audibly, tension crackled. Everard sought to bleed it off. “Don’t worry,” he said. “Things aren’t that delicately balanced in practice. The continuum is seldom easy to distort. For instance, in the case of you and your parents, your common sense would be a protective factor. Prospective time travelers are pretty carefully screened before they’re allowed to take off unsupervised. And most of what they do makes no long-range difference. Does it matter whether you or I did or did not attend a play at the Globe Theater one of the times when Shakespeare was on stage? Even if, oh, if you did cancel your parents’ marriage and your sister’s life—with all due respect, I don’t think world history would notice. Her husband-who-would-have-been would marry somebody else, and the somebody else would . . . happen . . . to be such a person that after a few generations the gene pool would be the same as it would have been anyway. The same famous descendant would be born, several hundred years from now. And so on. Do you follow?”

  “You’re throwing me curve balls till it’s my head that’s spinning. But, oh, I did learn a little about relativity. World lines, our tracks through space-time. They’re like a mesh of tough rubber bands, right? Pull on them, and they’ll try to spring back to their proper, uh, configuration.”

  He whistled softly. “You do catch on fast.”

  She wasn’t relieved in the least. “However, there are events, people, situations where the balance is . . . unstable. Aren’t there? Like if some well-meaning idiot kept Booth from shooting Lincoln, maybe that’d change everything afterward?”

  He nodded.

  She sat straight, shivering, and gripped her knees. “Don Luis wanted—he wants to get hold of modern weapons—go back to Perú in the sixteenth century and . . . take charge of the Conquest, then stamp out the Protestants in Europe and drive the Muslims out of Palestine—”

  “You’ve got the idea.”

  Everard leaned farther forward and caught her hands in his. She clung. Hers were cold. “Don’t be afraid, Wanda,” he urged. “Yes, it is terrifying. It could turn out that you and I never had this talk today, that we and our whole world never were, not even a dream in somebody’s sleep. It’s harder to imagine and harder to take than the idea of personal annihilation when we die. How well I know. But it isn’t going to be, Wanda. Castelar is a fluke. By a freak of chance, he got hold of a timecycle and learned how to operate it. Well, he’s one man alone, otherwise ignorant; he barely escaped from here last night; the Patrol is on his trail. We’ll nail him, Wanda, and repair any damage he may have done. That’s what we’re for. Our record is pretty damn good, if I do say so myself. And I do.”

  She gulped. “Okay, I believe you, Manse.” He felt warmth begin returning to the fingers between his.

  “Good girl. You’re helping us a lot, you know. Your account of your experience was excellent, full of clues to what he’ll try next. I expect to gather more hints as new questions occur to me. Quite likely you’ll have suggestions of your own.”

  Further reassurance: “That’s why I’m being this open with you. As I told you earlier, ordinarily it’s forbidden to reveal to outsiders that time travel goes on. More than forbidden; we’re conditioned against it, we’re unable to. But these are rather special circumstances, and I’m what they call an Unattached agent, with authority to waive the rules.”

  She withdrew her hands, gently but firmly. Cool customer, he thought. I don’t mean frigid. Independent. Guts, backbone, brains. At twenty-one years of age. Her look upon him cleared, and the slightly husky voice was again steady, unstrained. “Thanks. Thanks more than I can say. You’re rather special yourself, you know?”

  “Naw. I simply happen to be the operative working on this case.” He smiled. “Too bad you didn’t draw a hotshot glamour boy, like maybe from the Planetary Engineers milieu.”

  “The what?” She didn’t wait for a reply. “I gather the Patrol recruits in all periods.”

  “Well, not exactly. Prior to the scientific revolution around 1600 A.D., persons capable of imagining the idea are few and far between. Castelar’s an extraordinary guy.”

  “How did they find you?”

  “I answered an ad and took some tests, back in—well, it was a while ago.” Not to say “1957” flat out. Why not? Because she doesn’t have the whole background. She’d think of me as ancient. . . . And why should that matter, Everard, you old goat? “Recruits are found in many different ways.” He stirred. “Look, I realize you have ten million questions, and I’d like to answer them for you, and maybe later I can. But right now, could we get on with business? I want more details of what happened. Time is short.”