The US Navy CH-53E Super Stallion hovered above the helipad on USS McKee's afterdeck, navigation lights twinkling as it sank slowly onto the brightly lit landing circle, and Mordecai Morris made himself sit motionless in its red-lit, noisy belly by sheer force of will.

He turned his head and smiled at Jayne Hastings. Did he look as unnatural in his flight suit and helmet as she did? He was certain he looked equally tired, at least, he thought, running his aching mind back over the journey which had brought them here.

On the face of it, the whole thing was preposterous, and only the fact that Admiral McLain also knew Dick Aston could account for it. Even so, he'd been incredulous and a bit incensed by the paucity of the information Morris had for him. In the end, though, CINCLANT had agreed that if there was the slightest possibility Aston really was onto something the trip had to be made, and things had begun to roll.

Their original plan to fly out on an Air Force B-1B scheduled for a training mission to Britain had been scrubbed when the South Atlantic suddenly turned hot. Morris shook his head sadly, wondering what had gone wrong. He had many contacts in the Royal Navy, and he'd been positive the Brits contemplated no offensive action. But something had hit the fan down there, and the Argentinean charges of unprovoked attacks and the massacre and mutilation of prisoners sounded ugly, indeed. It was too bad the US hadn't had a recon bird up to see what was going on for itself, but it appeared that the first the Brits knew of it had been a sudden, totally unexpected strike on one of their LPH assault ships by a quartet of the Mirage 2000-5s which had finally replaced the venerable Super Entendards as Argentina's primary launch platform for the Exocet.

HMS Ocean had been on station off the Falklands with the better part of a full battalion of the Royal Marines on board when the surprise attack caught her at sea. Her close-in defenses had managed to stop two or three missiles, but the others had gotten through. She'd simply blown up, and, in the face of horrible casualties, the UK had responded in strength. The reports were still coming in, filtered to him through Navy channels even out here, but it sounded like the tanker-supported Tornado squadrons the RAF had deployed three months ago were beating holy hell out of the Argies' airfields. The reports indicated the Brits' decision to base a pair of E-3D AWACS aircraft on Port Stanley was paying dividends, too; they'd apparently hacked over thirty Argy attack planes and fighters out of the sky in the past twelve hours.

But the sudden carnage had captured the Air Force's attention—especially when Argentina indignantly accused the US of complicity in the initial British attack. And if their claims were accurate, they had a point, Morris admitted unhappily, for the US diplomatic corps and intelligence agencies had assured Buenos Aires that no British offensive action was planned. At any rate, the Air Force had decided to keep the big bombers closer to home.

The shooting in the South Atlantic made this a terrible time for CINCLANT's top intelligence types to be elsewhere, yet Admiral McLain had not wavered. He had a battle group built around the carriers Nimitz and Washington heading south just in case, but he'd sent Morris and Hastings off anyway. In default of the B-1, he'd put them aboard an S-3 Viking, and the carrier-based antisub aircraft had delivered them to the RAF airfield at Stornoway, Scotland, after a five-hour flight which would live forever in Morris's memory. The terrible weather had given him a whole new respect for the men who flew patrols aboard the four-place aircraft, and the fact that the flight crew were not allowed to ask questions about the absence of their normal tactical crew hadn't made the flight a particularly sociable experience.

At least the weather had improved as they approached the British Isles, and the helicopter flight from Stornoway to Holy Loch wouldn't have been too bad, except for the fact that helicopters had to be the noisiest form of transport yet invented by man. Every muscle ached, and the stump of his right leg throbbed. Dick had better have a damned good reason, Morris thought with yet another stab of resentment and anticipation.

* * *

"They'll be down in about ten minutes, Milla," Aston warned.

Ludmilla looked up from the paper wreckage littering Lieutenant Shu's cramped office and shrugged. She looked completely rested, he thought with just a trace of jealousy. She was clear-eyed and her face was relaxed—in sharp contrast to his own red-rimmed eyes and tension. She'd made him shower and shave, and his body appreciated the sense of freshness, but he knew it was false energy.

"I'm about as ready as I can be," she said calmly. She turned her head and smiled; Lieutenant Shu was bent over her desk, head pillowed on her folded arms, and a faintly audible snore came from her. Ludmilla rose quietly, took Aston's elbow, and led him back to the isolation section without disturbing the doctor. An armed Marine corporal followed them, then joined the sentry already there.

"You're sure you can decide without the doc?" Aston asked as soon as the door closed behind them.

"Positive," Ludmilla said confidently, then qualified her statement. "Or let's say as positive as I can be. There's an element of risk, but I think it's acceptable. It'll have to be, won't it?" Her clipped accent had sharpened, burning through the carefully cultivated softening she'd worked on so hard. It was the only sign of anxiety she showed.

"What's the verdict to date, then?"

"Admiral Rose is safe," Ludmilla said, "but not Captain Helsing. Nor, I'm sorry to say, is Doctor Shu. The XO is all right, and so are most of the Marine officers." She shrugged again. "Other than that, the numbers seem about what they'd've been back home. It looks like thirty-six of the hundred and ten we tested could be picked up by the Troll."

"Um. At least Jack's okay," Aston said, rubbing his bald pate wearily. "If worse comes to worst, we can tell him even if we can't tell M&M or Commander Hastings."

"Don't borrow trouble, Dick. We'll know soon enough, and then—"

She broke off as someone knocked quietly on the hatch.


Mordecai Morris was impressed by the security Aston seemed to deem appropriate. The decks were deserted, as were the passages between helipad and sickbay, but McKee's Marine detachment was in evidence—and armed. Not just with side arms, either.

Their Marine lieutenant guide stopped outside sickbay, and the two sentries there came to attention as he knocked on the hatch.

"Enter," a deep voice called, and the lieutenant opened the hatch and stood aside. Morris and Hastings exchanged speaking glances as they passed between the armed guards, then turned their attention to the two people awaiting them.

They both recognized Aston, and Morris was struck by his exhaustion. He looked spruce enough, but his eyes were red and swollen and his face was weary. He was in civilian dress, but the young woman—girl, rather—sitting on the edge of the bed wore a weird combination of Navy dungarees and one of those gaudy, silk-screened tee-shirts Morris loathed and abominated.

He was surprised to find anyone with Aston, and that prompted him to give the girl another, longer look. She returned his regard levelly, with neither uncertainty nor the arrogance some teenagers used to mask any lack of assurance, and she was a good-looking kid. Not beautiful, but striking—especially with those incredible blue eyes. A little more muscular than he liked, but, then, he was indolent by nature.

"Mordecai," Aston said, and extended his hand. Morris felt the big, calloused hand envelop his with its customary combination of crushing strength and careful restraint and hoped he looked less worn out than Aston.

"Dick." He squeezed back, then nodded to Hastings. "You know Jayne Hastings, I think?"

"We've met." Aston extended his hand to the lieutenant commander in turn. She smiled, but her green eyes burned behind her glasses.

"All right, folks," Aston continued more briskly, "before we do anything else, we need to see your EEGs."

"Dick, what the—"

"Bear with me, M&M," Aston said softly, and Morris was surprised by the almost entreating note in his powerful voice. That silenced him, and he opened his briefcase and dragged out several folded sheets of paper.

"All right, Dick," he sighed. "Here. And Admiral McLain figured it might be as well to send his along, too."

"He did? Four-oh!" Aston exclaimed. "I knew you were a persuasive bastard!" He took the EEGs and, to Morris's surprise (though why anything should surprise him at this point eluded him), handed them to the girl. "Here, Milla," he said, and Morris made his eyebrows stay put despite the odd gentleness in Dick's voice. Could he—? No! It was preposterous.

The girl sat cross-legged on the bed and spread the charts over her lap. She looked like a Girl Scout practicing origami, Morris thought, but her smooth young face was intent. She ran a rosy fingertip across the first graph, clearly searching for something, then set it aside to check the second. Then the third. She looked up at Aston and drew a deep breath, her eyes brightening with what could only be relief, as she nodded.

"Clean sweep," she said softly. "All three of them."

"Thank God," Aston murmured reverently, and sank into the chair by the bed. Morris stared at him in consternation as he rubbed his bald head. It was a gesture Morris had seen often, but Aston's rock-steady fingers had never trembled before, not even after the firefight in Amman.

"Dick?" His friend's reaction had banished his last frustration. The pressure under which this ill-assorted pair labored was too obvious.

"Sorry, Mordecai." Aston shook his head and managed a tired smile. "You'll be pleased to know that you two—and Admiral McLain—belong to a select group. One cleared for the whole story, as it were. Sit down."

He gestured at the extra chairs crowding the small compartment, and the intelligence officers sat wordlessly, staring first at each other and then at him.

"People," he said slowly, "we've been invaded." He saw their shoulders stiffen and grinned tiredly. "In fact, we've been invaded twice—once by the bad guys and once by the good guys. Unfortunately, it looks like the bad guys have the force advantage, and, unless we can figure out how to turn things around, we're all in one hell of a mess."

He had their undivided attention, and the absurdity of the situation appealed to his sense of humor. He repressed an exhaustion-spawned urge to giggle and cleared his throat, instead.

"Commander Morris, Lieutenant Commander Hastings, allow me to introduce the good guys," he said, waving a hand at Ludmilla. "This is Colonel Ludmilla Leonovna, people—not a Russian," he added quickly, seeing the same initial assumption in both pairs of eyes and remembering his own first reaction. Amusement strengthened his voice. "Not even a Terran, really. You see, she comes from Sigma Draconis. . . ."


" . . . so that's the story," Aston finished three hours later, and the intelligence officers shook their heads in unison. The tale he and Ludmilla had told was incredible, preposterous, impossible to believe . . . and carried the unmistakable ring of truth.

"Dear God," Morris said softly, speaking for the first time in over half an hour. "Dear sweet God in Heaven."

"Amen," Hastings said, equally softly, but there was worry in her eyes. She rubbed the tip of her nose gently for several seconds, then glanced sharply at Ludmilla.

"Excuse me, Colonel—" she began.

"Please, Ludmilla. Or Milla," Ludmilla interrupted.

"All right, Ludmilla," Hastings agreed. "But I've got two burning questions for you."

"Only two?" Ludmilla asked with a crooked smile.

"Two immediate ones," Hastings acknowledged with a shadow of an answering smile. "First, and most pressingly, there's the matter of this symbiote of yours. You say it's transmitted by direct blood transfer?"


"Then I think we have a problem," Hastings said softly. "Possibly a very serious one." Ludmilla raised an eyebrow, inviting her to continue. "Mosquitoes," Hastings said softly, and felt Morris stiffen beside her.

"Don't worry," Ludmilla said quickly. "Believe me, the Normals of my own time worried about the same thing, but we never found a single instance of transmission by any insect or vermin vector."

"Why not?" Hastings asked sharply.

"Two reasons," Ludmilla replied imperturbably. "First, our symbiotes don't seem to approve of insect bites; they exude a sort of natural insect repellent. But the second reason is even more effective. It takes the average human a little less than twelve hours to go into crisis if she's infected with the symbiote, but it acts a lot faster on smaller life forms and none of them survive. Any bug that bites me will be dead before it gets its proboscis out of my bloodstream. It'll never live long enough to transmit it to anyone else."

"Oh." Hastings mulled that over for a moment, then nodded slowly. "But what about insects on your home planet?" she asked curiously. "If they're immune because of their different amino acids . . . ?"

"Commander Hastings," Ludmilla said gently, "one of Midgard's main tourist attractions is that the local insects don't like the taste of humans."

"That would be an attraction," Hastings agreed with a smile, and Ludmilla felt her spirits rise. That smile carried acceptance as well as amusement. For a moment, she'd been afraid Hastings was going to turn paranoid on her. She'd seen too many people of her own time do exactly the same, and with far less reason.

"But you said you had a second question?" she prompted after a minute.

"Oh, yes! I don't pretend to be an expert, but it occurs to me that this whole thing represents a causal nightmare."

"I couldn't agree more," Ludmilla said sincerely.

"Well, if we accept causality at all, then it sounds to me like we're faced with the disagreement between the Copenhagen school and the Many-Worlds interpretation," Hastings said. "The whole question of what happens when the superposition collapses and—"

"Jayne," Morris said sternly, "I've warned you about talking gibberish."

"Oh, hush, Mordecai!" his disrespectful junior shot back, but she paused. "All right, in simple terms the problem is how Colonel Leonovna—Ludmilla—and this Troll creature can change their own past. On the face of it, the very notion negates the entire concept of causality."

"The old `can I kill my grandfather' thing?" Morris mused.

"More or less. The point is, what's happening represents a significant alteration to history. Ludmilla, did your records contain any mention of what happened to Task Force Twenty-Three?"

"No. And my hobby interest was military history. If there'd been any record of an authenticated attack on any Terran military force by UFOs, I'd've known about it, believe me."

"So we already have a gross shift in your history," Hastings pointed out. "Presumably, the effort we'll have to mobilize to do anything effective about this Troll will have an even greater effect. If nothing else, we know these Kanga creatures exist." She smiled unpleasantly. "Knowing that, I think we can confidently assume that their reception will be even more energetic than it `was' in your own past. But the end result will be that your universe will never come into existence at all!"

"I know," Ludmilla said softly.

"But if it doesn't, then you won't come back, and if you don't come back, then it will," Morris said slowly, rubbing his forehead as he tried to understand. "What do we have here—some kind of loop?"

"That's where the Many-Worlds Theory comes in," Hastings said. "But even if Everett was right—" She shook her head. "I don't even know where to start looking for questions, much less what the answers might be!"

"Neither does anyone where I come from," Ludmilla said wryly. "Look, the whole theory behind a Takeshita Translation is just that: theory. No one's ever tried one—or reported back afterward, anyway—and the argument over what ought to happen during one has gone on for a century and a half.

"Jayne, you mentioned the Copenhagen School and the Many-Worlds Theory. We don't use that terminology anymore, but I know what you mean, and the fundamental problem remains, because there's still no way to test either theory." Aston and Morris looked utterly confused, and she made a face.

"Bear with me a minute, you two," she said, "and I'll do my ignorant best to explain, all right?" They nodded, and she went on.

"In its simplest terms, what Jayne is talking about is one of the major problems involved in understanding quantum mechanics. There's been a lot of progress since the twenty-first century, but I'm just a fighter jock." She used Aston's terminology with a wry grin.

"Essentially, there's been a dispute over the basic nature of what we fondly call `reality' almost since Einstein. According to the math, any possible interaction—or, rather, the result of any interaction—is a superposition of functions, each of which represents one possible outcome of the interaction. With me so far?"

"Are you saying that mathematically speaking any of the outcomes is equally valid?" Aston sounded skeptical, and she patted his bald pate playfully.

"For a nullwit, that's not bad," she said teasingly. "Not quite right, but it'll do for starts. You see, the problem is that for any interaction, we observe one—and only one—outcome, but the math says the potential for all possible outcomes is bound up in the event. Now, what Jayne is calling the Copenhagen School says that at the moment a wave function—" She paused and grimaced, then resumed as if re-selecting her words. "Well, at the moment an interaction occurs, the whole thing collapses into a single one of the elements of possibility, and the others never come into existence at all. The potentiality of all outcomes remains up until that moment, and none of them can be absolutely ruled out, but a weighted probability distribution can be assigned to them, which allows the effective prediction of which single event will actually occur. Follow me?"

"Yes, but I'm losing a little ground. How about you, Mordecai."

"Quit asking me to expose my ignorance. You were saying, Colonel?"

"All right. An alternative hypothesis, proposed sometime in the last century, says, simply, that rather than a single event, all possible outcomes occur, however `probable' or `improbable' they may be. We observe only one, true, but that's because the others occur on different `stems' of reality."

"Parallel worlds, right?" Aston nodded. "Our sci-fi writers love 'em."

"They still do back home," Ludmilla assured him. "Anyway, Jayne's Copenhagen School—we call it the Classic School—maintains that there is one and only one reality; a single, linear reality in which the single realized outcome of each interaction is defined and creates the preconditions for the next. What we call the Revisionist School—Jayne's `Many-Worlds' theory—has gained a tremendous amount of ground in the last couple of hundred years, though, and some of its proponents claim that eventually they'll be able to demonstrate its validity through some esoteric manipulation of the multi-dee. I've seen the math on it, and it gives me headaches just to think about it; I certainly don't understand it. But the Revisionist School says that instead of a single reality, there are multiple realities, all branching off from a common initial source, all equally `real,' but never interfacing."

"So where does all this fit into time travel?" Aston asked, but a gleam in his weary eyes suggested that he saw where she was headed.

"There are three main theories as to what happens in a Takeshita Translation," Ludmilla said. "One says that the whole thing is impossible; anyone who tries one simply goes acoherent and stays there. It's neat, at least, but my survival is empirical evidence that it doesn't work.

"Theory number two is Takeshita's First Hypothesis, and it says that anyone making a Takeshita Translation travels backward along the single reality stem of the Classic School. There are some problems with it, but, essentially, it says that when the traveler stops moving—drops back into phase with reality, as it were—he becomes an event which has been superimposed upon the reality stem. He, personally, exists, wherever he came from and however he got there. But since he exists, he can affect the universe, which will inevitably affect the nature of reality `downstream' from him, with the result that—as Commander Morris put it—you really could murder your grandfather without erasing yourself. Your existence is pegged to a reality which preexists the one in which you were never born.

"Takeshita spent years on the math to support that theory, but in the last years of his life he became convinced that the Revisionists had been right all along, which created a furor amongst his followers, I can tell you! Anyway, he propounded his Second Hypothesis, which says, essentially, that the classic arguments against paradox are valid after all—that it's impossible for an individual to move into his own past. By the act of moving backward in time, he does, indeed, superimpose his existence on events, but, in the process, he causes the stream of reality to split off another tributary. In effect, he avoids paradox by forcing a divergence of `his' subsequent personal reality line from the one which created him.

"The problem, of course," she ended with a whimsical smile, "is that no hard experimental data was ever available. Until now, that is."

Silence threatened to stretch out indefinitely until Jayne Hastings finally broke it.

"So which theory's correct?" she asked softly.

"Let's start with the basics," Ludmilla suggested. "I am here—and so is the Troll. Task Force Twenty-Three was attacked and did shoot down two Troll fighters. Those facts seem to prove that whatever happened is possible, and, further, that the Troll can do whatever it intends to do unless we stop it. Those are the pragmatic considerations. Agreed?"

Three heads nodded, and she went on.

"All right. My own feeling is that Takeshita's Second Hypothesis applies, which means that the Revisionists were right, of course. And it also means that I'm not in my past, which neatly explains the absence of any recorded nuclear attack on a US Navy task force in 2007. It didn't happen in my reality—it happened in yours."

"You mean . . . you're not just from the future, you're from someone else's future?" Aston sounded a bit shaken.

"Why not? Nick Miyagi could have explained it a lot better—he always did support the Second Hypothesis." Ludmilla smiled sadly. "He almost took time to argue the point with me when we saw it happening. But, yes, that's right. I'm not from your reality—your `universe'—at all, Dick."

"But . . ." Hastings frowned as she worked through the implications. "Excuse me again, but you seem to be saying you more than half-expected the Kangas to wind up in somebody else's past."

"I did."

"Then why try to stop them?" Hastings asked very quietly. "You say your battle division was totally destroyed, along with thousands and thousands of your people. Your own fighter squadron was destroyed—in fact, you're the only survivor from your entire force. Why in God's name take such losses when these `Kangas' couldn't even hurt your time line at all?"

"Two reasons, really, I suppose," Ludmilla said after a moment. "First, of course, we couldn't be certain. Remember, Takeshita offered two hypotheses, and neither had ever been tested. What if he'd been right the first time, and the Kangas had changed our own history?" Hastings nodded slowly, but the question remained in her eyes, and Ludmilla smiled sadly.

"Then there was the second reason," she said softly. "Whoever's past they wound up in, we knew there was going to be a human race in it. Not our own ancestors, perhaps, but still an entire planet full of human beings. Commodore Santander and I never actually discussed it, but we didn't have to. We know what Kangas and Trolls are like. There was no way we could have lived with ourselves if we'd let them murder our entire race in any time line."

Silence hovered in the compartment, and Aston reached out to clasp her hand. She returned his grip tightly enough to hurt—tightly enough to give the lie to her calm expression—and his heart ached for her. She wasn't simply adrift in time; she was adrift in a totally different, utterly alien universe, where none of the worlds she'd known would ever even come into existence. And she was the one—and only—creature of her kind who would ever exist here.

She looked at him for a moment, then smiled. He recognized the courage behind that bright, cheerful expression, but no hint of her total aloneness showed in her voice as she looked back at Hastings.

"And wherever I am, and however I got here, Commander, you've got a Troll on your hands, don't you?" Hastings nodded, and Ludmilla shrugged. "Well, that's something I understand in anyone's universe, and killing Trolls is what I do. So what do you say we put our heads together and figure out how to kill this one."