Edward Markham opened one eye.

The universe slowly spun, reshaping and reforming around him. He was formless, a void. He didn't know who he was, or where, or when. How and why had left the building without stopping to ask for directions. His head and heart pounded in unison, as if he'd been on an all-night bender, and the blood roared in what presumably were his ears.

Consciousness returned, along with memory.

After what might have been seconds, or centuries, he realized he was lying full length on the floor of his own bookshop. He knew it was his bookshop—here was the same free-standing shelf crammed with vintage crime novels in lurid jackets, there the tattered edge of the frayed Oriental carpet, the same familiar feel of floorboards worn smooth by generations of feet.

The light looked wrong though; it was too bright, too diffused, coming from all the wrong angles. Markham blinked, trying his eyes out. It seemed to him as he slowly moved head and limbs, testing for injury, that the walls were further away than they ought to be. It must be some after-effect of…whatever had happened to him, after he touched the things. Wormholes, Bishop had called them.

Bishop! He'd know what was going on. Markham sat up abruptly, whispering the name through dry, chapped lips. His throat burned and his head swam; Markham swayed, and sank to the floor again. His right hand touched something; it turned out to be the handle of his trusty Louisville Slugger. He gripped it, finding comfort in the familiar feel of the smooth ash wood under his hand. He lay a few more minutes, breathing steadily and fighting nausea, before trying again, pushing himself up first on one elbow, then on both, till he was sitting more or less in an upright position.

Now to look around. Left…right…good. Markham froze in mid neck swivel as he saw that the room was subtly yet significantly different. The bookcase looked newer, for a start, made of some heavy, plastic-like material rather than the familiar dark oak. The carpet, no longer tattered and worn thin, had been expertly repaired, and appeared as bright and fresh as the day it was woven. And yes, the walls were further away—in fact, Markham noted to his astonishment that an entire side wall had been removed, expanding the bookshop to the whole lower level of the building. It was something he'd always dreamed of doing; the Big Time, yet somehow he'd never managed to save up the cash to get it done. And the dry cleaner next door had made it clear that he'd never sell.

Markham wobbled to his feet, using his bat as a cane, and gaped around him in growing awe and amazement. The books looked the same; there on the shelf in front of him sat The Corpse Steps Out, yet the whole shop was clean—cleaner than he'd ever had the time or inclination to get it. The windows positively sparkled, the floor was polished and waxed to within an inch of its life, and the slowly revolving ceiling fan wafted a faint whiff of citrus oil throughout the room. The walls had been painted a fashionable shade of burgundy with cream trim, and glowed under brilliant track lighting. From a short distance away came the sounds of clinking plates and glassware mingled with bright laughter and cocktail party chatter.

"What in the name of…?" Markham glanced down at his left hand, which, he saw, was still clutching the copy of The Corpse Stays In that had so disturbed him earlier. Frowning, he opened it and flipped through the pages. The characters were the same, yet the story was slightly altered from the one he knew. He snatched its almost-twin from the shelf and gave it a quick once-over, confirming that here was the same familiar old story he'd read many times before. "Come to Papa, baby," he murmured, and almost without thinking, pocketed both volumes. Somebody, he thought, had a lot of questions to answer.

And looking around at the shelves, Markham discovered something else. His shop had always contained a mixture of vintage and modern books, the old and the new, current bestsellers jostling for space with obscure volumes of the eighteenth and nineteenth centuries. Yet in this brightly-lit, sparkling, Bizarro version of his shop, he could see nothing that was less than thirty or forty years old.

"Bishop." His voice had come back. Good, that was a start. Time to get some answers. "I'm fine, kid, thanks a lot for asking. Hey, Bishop, what the hell is…" Markham rounded the corner to confront the man standing there and for the second time his voice died in his throat.

He was looking at himself.

Like everything here, his double was the same, yet different. Instead of a comfortably threadbare old sweater and baggy corduroys worn smooth at the knees, this Edward Markham wore a pricey salmon pink silk shirt under an elegant, hand-tailored suit that looked like it might be Armani. Above fashionable narrow spectacles his hair was sleek, shiny, and full. A multi-carat diamond stud gleamed in one earlobe. One manicured hand twirled a champagne glass, while the other performed complicated computations on some kind of oversized tablet computer.

And the customers! They filled the central area, winding in a long line from the counter to the door and down the street as far as the eye could see. Everywhere Markham looked, people were browsing through books, buying books, sipping champagne, and nibbling sophisticated little hors d'oeuvres plucked from trays carried by smiling waitresses. Most of them, Markham saw, carried iPad-or-tablet-things like the one his double was using. Off to the left, a large poster mounted on an easel announced that today, local author Katherine Anne Sheehan would be reading excerpts from her new novel, A Murder in Fringe Division. At a long, low table, a smartly-dressed woman of middle age, presumably Ms. Sheehan herself, sat signing everyone's tablets with some kind of electronic stylus. Every time she scrawled her signature, it made a bzzzt sound.

As Markham gazed wide-eyed at all the activity around him, his double turned and saw him. Just for a moment the two men stared at each other, caught up in awestruck astonishment, unable to speak or even move. Then, all at once, the moment ended. The other Markham was the first to recover; setting down his tablet, he strolled forward to greet his latest visitor.

"I'm going to go out on a limb here," this almost-doppelganger drawled, "and guess that you aren't my long-lost twin brother Edgar Markham, separated from me at birth and abandoned at Back Bay Station in a handbag."

"You got that right," Markham recovered enough to say. He managed a few tentative steps forward, wondering what the etiquette was for this type of situation. So, unless I hit my head harder than I thought, this must be that parallel universe place I've heard so much about. Pleased to meet me. His twin said it for him.

"You're me, aren't you?" he asked. "From another universe. One hears stories, of course, but I never believed it was even possible till now. How did you cross over? Did it hurt? You look a trifle…disheveled."

Markham licked dry lips. Bishop wasn't crazy, he thought. It's all real. "You know about other universes?" He didn't mention he'd only heard about them himself this morning.

"As I said, I've heard stories. Whispered hints, circulating for years now. Mostly among the more lunatic fringe, who use them as a scapegoat for everything from sheep going extinct to male pattern baldness, but about a year ago the rumors really started to fly thick and fast. Supposedly, some government higher-ups kidnapped a woman from the other universe and replaced her with her double from here. Meant to be top-secret, of course, but these things have a way of getting out. It's why I don't set much store by conspiracy theories—most people just aren't capable of keeping their mouths shut."

"Then you didn't bring me here?"

"I just sell books." His double spread his hands in a self-deprecating gesture. He smiled, but his eyes remained wary. "Do I look like a theoretical physicist?"

"Well, someone did, and it sure as hell wasn't me," said Markham. He looked around, blinking in the unaccustomed brightness of the shop. "Not to mention, they're screwing with the books, and they're gonna answer to me for that. Where's Bishop? Is he here?"

"Bishop?" The other Markham raised an eyebrow. "The only Bishop I know is the Secretary of Defense, and when I say 'know', I mean by reputation only. Never met the man in person, though I understand we share the same tailor." He smirked a little, flicking an invisible speck of dust from one immaculate cuff. "May I ask what you meant by 'screwing with the books'? I assure you my store accounts are entirely in order, though what concern that might be of yours-"

"Not that kinda books." Markham just managed not to add "dipshit" at the end. No point in antagonizing…himself, though for him fear always manifested as anger, and he could feel the first prickling of panic sliding icy fingers along his spine. If Bishop hadn't followed him here, where the hell was he? Was it possible that he, Markham, might be trapped in Bizarro Universe for all eternity? No. No, he refused to believe that. Bishop would come through for him. Together, they'd find a way back…

"This," he said, pulling out the two paperbacks from his sweater pocket and brandishing them at his double. "They got switched somehow, right before I…crossed over. And it ain't the first time, either. It's been happening with lots of different books; a word here and there, a character, a picture, maybe—and it's hurting them. They don't like it." He paused, feeling slightly foolish revealing this aspect of his inner life to this elegant stranger with his face. He didn't like playing straight man to anyone, and was struck by a sudden, insane fear that his double might laugh at him, or worse, think he was crazy.

"Two objects cannot occupy the same space," his double murmured, studying the two books, turning them over and over in his manicured hands. "Something has to give. Look at this. It's extraordinary. Even the covers are mirror images of each other. And it's happened before, you say? I wonder…that could explain why…" his voice trailed off.

"Explain what?" Markham demanded.

"Why Fringe Division sent one of their agents out here three times in the last week. Some sort of energy spike, she said, but it always disappeared by the time she got here. Finally, she wrote it off as an equipment malfunction, but perhaps it was you, all along, trying to cross universes." His voice softened, turned reminiscent. "Agent Dunham, her name is. A feisty redhead. Likes Vonnegut and Stephen King. I wouldn't kick that one out of bed for eating…well, anything, if you get my drift." He wiggled an eyebrow suggestively.

Talk about deja-vu, Markham thought. Maybe we're more alike than I thought. "And I'm telling you, I ain't the one doing this." He returned with decision to the topic at hand. "I didn't come here to Book Club Med for no holiday. I was dragged here when I touched a...well, Bishop called them bookworms. Big, transparent snaky things. They're eating holes in reality. Bishop says they're a byproduct of travel in the fourth dimension, and I figure that's as good an explanation as any."

"Time travel?" His twin looked startled.

"That's what the fourth dimension is, ain't it? Somebody's screwing around with time, and they've been doing it for a while now. Look, I know books, and I'm guessing you do too, since we're the same guy, in a sense, and when you get a whole bunch of 'em together, things get…funny. I've known that for a long time. But lately—things are getting funnier, and not in a ha-ha way. It's hurting the books. Eating away at them, destroying their sense of self. I hear them talking, at night-"

"You what?" The other bookseller stared at him for a moment, an odd expression on his face. For a minute Markham thought he was going to call for the boys in white coats, but then he let out a long breath that was almost a sigh. "You've heard it too? Thank God—I thought I was losing my mind. I thought when I finally moved out of that ghastly apartment upstairs it would all go away, but it's only gotten worse." He turned on his twin, his face suddenly full of grim determination. "Markham, we have to stop—whoever is doing this."

"No shit, Sherlock."

"Who?" his double asked, frowning. "How do you suggest…?" Markham was about to ask how in hell was he supposed to know, when they were joined by the most stunning brunette he'd ever seen. Tall, with generous curves in all the right places, she wore a short black jersey cocktail dress, cut low and tight. She had fashionable blonde streaks in her shiny brown hair, and looked like every late-night fantasy Markham had ever had. She put her arm intimately around the other Markham and smiled sweetly down at him.

"Eddie, sweetheart, Kate's ready for you to introduce her-" she began, and then caught sight of Markham, who was standing with his mouth stupidly agape. She gave a small shriek, stepping backward and almost tripping over her spike heels, one hand to her mouth.

Markham took a second look, and a third, and almost had to restrain a shriek himself. For the brunette was none other than Jill Moss, PHD candidate in genetics and world-class baker; Jill, whom he had never in his life seen wearing anything except baggy cargo pants and t-shirts with local indie bands on them. He'd never entertained any fantasies about that Jill or even thought of her as a remotely sexual being; couldn't imagine her wearing makeup and fuck-me pumps and patterned lace stockings. Or for that matter, shrieking like a starlet in a horror flick.

Eddie Markham put a proprietary arm around this vision's waist, then moved his hand down to her ass. "In a minute, baby," he said. "I'm just chatting with my, er-"

"You're—he's—you're-" Jill sputtered, wide-eyed, index finger wavering between the two men.

"Edgar Markham," said the otherworlder hastily, before Eddie gave the game away. "From Schenectady. We're cousins, identical cousins," he added, and gave a lopsided leer.

Jill looked politely blank—maybe they didn't have The Patty Duke Show in this universe, or she was just too young to get the reference—but she took his outstretched hand anyway. "It's a pleasure, Edgar. Wow, the resemblance is really amazing."

"And this is Jill Moss," said Eddie, by way of introduction. "The finest business partner a guy could ask for. All this," –he waved a hand at their surroundings- "is Jill's doing. Three years ago, I was down and out—ready to throw in the towel and take an entry-level job stocking shelves at S-Mart, but Jill convinced me to risk everything and put all my savings into expanding. Turn the shop from a dingy little hole into a real first-class, twenty-first century operation. And she was right—it paid off in spades."

"And we became lovers," said Jill, gazing sappily down at the bookseller. He returned her glance and they made kissing motions at each other.

Just stick a finger down my throat and bring me a bucket, thought Markham. But before it could get any worse, Eddie broke the mood, pulling away from Jill and turning to face his double.

"You'll have to excuse me for a while, I'm afraid," he said. "Duty calls. Jill, dear, will you make sure our guests are seated for the reading?" When she'd moved away, he continued in a lower voice, "In the meantime, perhaps, you can make note of the books that have been—er, altered. I'm damned if I know what to do about this, but if we put both our minds to it, no doubt we can come up with a solution. This Bishop person you've mentioned—can he help?"

"If anyone can," replied Markham. "But he ain't here, and there's no guarantee he's gonna turn up any time soon. So I guess it's just us for right now."

"I wish I could say that inspired confidence," said Eddie, and turned to go. As an afterthought, he turned back to Markham. "Oh—please help yourself to hors d'oeuvres and beverages. We have guacamole," he pronounced in a tone in which someone else might have said, "We have Beluga caviar and Perigord truffles."

"Tex-Mex gives me gas," Markham answered, but he went to inspect the buffet anyway. Behind him, he could hear his double introducing Ms. Sheehan, who went on to thank a long line of individuals who had helped her book see the light of day, including her publisher, her husband, and an Agent Lee, who apparently had permitted her to do some kind of ride-along with his division.

As she began to read a scene of a shoot-out in a warehouse, Markham piled a small plate with finger foods and looked around in vain for the coffee urn. The closest he could find was a samovar full of hot water and a selection of tea bags. Champagne sounded more promising, until Markham saw that it came in a plastic box that read "Champagne-type beverage—contains up to 12% real grape juice", and he decided to give it a pass in favor of a mug of Rooibos.

His hands and mouth full of food and drink, Markham made himself as inconspicuous as possible among the shelves of the bookshop, scanning them for anomalous volumes. He felt useless, wondering what in hell he was doing, but soon his instincts regarding his own stock took over. Locating the books from his own universe—there were forty or fifty altogether—he piled them all up on a small table. Might as well have them all together when Bishop showed up—if he showed up—and they did…whatever. Kicked quantum ass. If he listened very closely, Markham could hear the books whispering to each other even now, their voices desperate yet muffled by the volumes piled on top of them.

He even found his copy of the Wicked Bible locked in the Rare Books cabinet behind the counter—wickedness intact, as he was pleased to note once he'd located the key in the same hidden desk drawer where he kept his own—and secreted it under his sweater. He was damned if he was going to let it get away from him again.

Meanwhile, Ms. Sheehan finished reading the scene at the warehouse, to much applause. She went on to read another selection, this time a steamy love scene between agents Kennedy and Warren. As the women in the audience giggled and blushed and fanned themselves, Markham found himself listening to her voice, absorbed in spite of himself. He wondered if she had a counterpart back home in his own universe, whether she was a writer, and what sort of books she wrote if she was. Presumably nothing involving Fringe Division, which according to Bishop was a top-secret organization, unknown to any but certain government higher-ups. Here, it appeared to operate more openly. He resolved to look her up if—no, when, he told himself firmly, when—he got back home.

It occurred to him that not only Ms. Sheehan, but everyone, every customer in the shop, had their own double, possibly infinite copies of themselves, living similar yet different lives in an infinite number of universes. Somewhere, here yet not here, just out of reach, thousands upon thousands of Edward Markhams were stocking shelves, waiting on customers, making love to infinite copies of Jill Moss. And every new thought, every emotion and decision of every person in the world created a new universe with billions of people thinking and feeling and deciding things every second that created more and more universes; infinite, never ending, spreading outward and outward over and over and over again…

It made his brain hurt just to think about it.

A metallic clang, as of someone falling over a metal folding chair, issued from the back room, causing both Markhams to turn in that direction. They gave each other surprised looks as they hurried to the back of the shop, followed closely by Jill.

As they all crowded in through the narrow doorway like the Three Stooges, Markham saw that the back room was much the same as his own, if quite a bit cleaner and more brightly lit. There appeared to be some subtle differences in the comics and manga, differences he would have liked to take a closer look at, but was distracted by the presence of-

"Bishop! Thank God!"

Markham barely restrained himself from throwing his arms around the younger man in relief, but settled for a punch as near to Bishop's shoulder as he could reach, instead. Bishop, he noticed, looked like crap. Ashen pale, with a sheen of sweat limning his face, bloodshot eyes and visibly trembling hands, he gripped the edge of the long table for support and gulped several deep breaths, as if willing himself not to throw up.

"Hey, Ed," he murmured, managing a nod in Markham's direction and looking like he regretted it immediately afterward. He caught sight of Eddie and did a double take. "Oh, man," he went on, half to himself. "Talk about surreal. This gives a whole new meaning to 'eddies in the space-time continuum'."

"A fellow Douglas Adams fan," Eddie Markham said, beaming approval. "I like him already."

"What're you guys doing back here?" Jill asked. "The party's out in front. Eddie, do you know these two?"

"Where the hell you been, Bishop?" Markham demanded, scowling, relief at seeing his friend again manifesting as anger. "And why'd you drag Emo Boy along with you?" he added, with a glance at Bishop's companion.

"This is Toby," said Bishop, pulling himself upright with some effort. "Our new best friend, who's going to get us back where we belong—isn't that right, Toby?" The kid with him looked in far worse shape, grey-faced and shaking all over as if from a fever. As Markham watched, his eyes crossed and he slid slowly down the wall to a sitting position. He covered his face with his hands and let out a long, shaky sigh.

"I never said I was going to help you." His voice emerged in a ragged whisper. "You dragged me here. At gunpoint. What's to stop me from just going back home and leaving you here?"

"Because," said Peter Bishop, "you're dying."