V
"I hope you realize," Garwood said heavily, "that by bringing me back you're putting everyone in Backdrop at risk."
Saunders raised polite eyebrows. Polite, stupidly unconcerned eyebrows. "Perhaps," he said. "But at least here we understand what's going on and can take the appropriate precautions. Unlike the nation at large, I may add, which you've just spent nearly four months putting at similar risk. Under the circumstances, I'm sure you'd agree that one of our concerns now has to be to keep you as isolated from the rest of the country as possible." He shrugged. "And as long as you have to be here anyway, you might as well keep busy."
"Oh, of course," Garwood snorted. "I might as well help Backdrop to fall apart that much soo—"
He broke off as a muffled cracking sound drifted into the room. "More of the plaster going," Saunders identified it off-handedly. "Nice to hear again after so long."
Garwood felt like hitting the man. "Damn it all, Saunders," he snarled. "Why won't you listen to reason? A working time machine cannot be made. The very fact that Backdrop is falling apart around me—"
"Proves that the machine can be made," Saunders cut him off. "If you'd stop thinking emotionally for a minute and track through the logic you'd realize that." Abruptly, all the vaguely amused patience vanished from his face, and his eyes hardened as they bored into Garwood's with an unexpected intensity. "Don't you understand?" he continued quietly. "When you left, the probability-shift damage to Backdrop dropped off to near zero. Now that you're back, the destruction is on the increase again."
"Which is my point—"
"No; which is my point," Saunders snapped. "The probability-shift effect cannot exist if a working time machine isn't possible."
"And yet that same effect precludes the manufacture of any such machine," Garwood pointed out. "As I've explained to you at least a hundred times."
"Perhaps. But perhaps not. Even given that the concept of time-travel generates circular arguments in the first place, has it occurred to you that a working time machine might actually prove to be a stabilizing factor?"
Garwood frowned. "You mean that if we have the theoretical capability of going back and correcting all these alterations of history then the wild fluctuations will subside of their own accord?"
"Something like that," Saunders nodded. "I did some preliminary mathematics on that question while you were gone and it looks promising. Of course, we won't know for sure until I have all the equations to work with."
"And what if you're wrong?" Garwood countered. "What if a working time machine would simply destabilize things further?"
A flicker of Saunders's old innocent expression crossed the man's face. "Why, then, we won't be able to make one, will we? The components will fall apart faster than we can replace them."
"In which event, we're back to the probability-shift effect being a circular paradox," Garwood sighed. "If it prevents us from building a time machine, there's no time travel. If there's no time travel, there's no change in probabilities and hence no probability-shift effect."
"As I said, time travel tends to generate paradoxes like that." Saunders pursed his lips. "There's one other possibility that's occurred to me, though. The man who brought you back from Champaign—Major Davidson—said in his report that you'd been trying to find an alternative solution to the time travel equations. Any luck?"
Garwood shook his head. "All I found was blind alleys."
"Maybe you just didn't get to look long enough."
Garwood eyed him. "Meaning...?"
"Meaning that one other possible explanation of the probability-shift effect is that there is indeed another set of solutions. A set that will let us build the machine and still be able to go back and change things."
Garwood sighed. "Saunders... don't you see that all you're doing is just making things worse? Isn't it bad enough that things fall apart around me?—do you want to see it happening on a global scale? Stabilization be damned: a time machine—a real, functional time machine—would be the worst instrument of destruction ever created. Ever created."
"All I know," Saunders said softly, "is that anything the universe allows us to do will eventually be done. If we don't build the machine, someone else will. Someone who might not hesitate to use it for the mass destruction you're so worried about."
Garwood shook his head tiredly. The discussion was finally turning, as he'd known it eventually would, onto ail-too familiar territory: the question of whether or not the fruits of Backdrop's labor would be used responsibly by the politicians who would inherit it. "We've gone round and round on this one," he sighed, getting to his feet. "Neither of us is likely to change the other's mind this time, either. So if you don't mind, it's been a long drive and I'd like to get some rest."
"Fine." Saunders stood, too. "Tomorrow is soon enough to get back to work."
In the distance, the sound of more cracking plaster underlined his last word. "And if I refuse?" Garwood asked.
"You won't."
"Suppose I do?" Garwood persisted.
Saunders smiled lopsidedly and waved a hand in an all-encompassing gesture. "You talk too contemptuously about the not-me' generation to adopt their philosophy. You won't turn your back on a problem this serious... especially given that it's a problem partially of your own creation."
For a long moment Garwood considered arguing the latter point. It had been Saunders, after all, who'd pushed Backdrop into existence and then dragged him into it.
But on the other hand, it wasn't Saunders who knew how to build the damn time machine.
Wordlessly, he turned his back on the other and headed for the door. "Rest well," Saunders called after him.
—
His office, when he arrived there the next morning, was almost unrecognizable.
Two pieces of brand-new equipment had been shoehorned into the already cramped space, for starters; a terminal with what turned out to be a direct line to the Minneapolis Cray HI supercomputer lab, and an expensive optical scanner that seemed set up to read typewritten equations directly onto the line. So Saunders is capable of learning, Garwood thought sardonically, careful not to touch either instrument as he gave them a brief examination. The electronic blackboard that had fallen apart shortly before he left Backdrop was gone, replaced by an old-fashioned chalk-on-slate type, and his steel-and-plastic chair had been replaced by a steel-and-wood one. Even his desk looked somehow different, though it took him a long minute to realize why.
All the piles of papers had been changed.
Silently, he mouthed a curse. He hadn't expected the papers to remain untouched—Saunders would certainly have ransacked his desk in hopes of finding the rest of his time-travel equations—but he hadn't expected everything to get so thoroughly shuffled in the process. Clearly, Saunders had gone about his task with a will and to hell with neatness; just as clearly, it was going to take most of the day to put things back where he could find them again. With a sigh, he sank gingerly into his new chair and started restacking.
It was two hours later, and he was not quite halfway through the task, when there was a knock on the door. "Come in, Saunders," he called.
It wasn't Saunders. "Hello, Dr. Garwood," Major Davidson nodded, throwing a glance around the room. "You busy?"
"Not especially." Garwood looked up at him. "Checking to make sure I'm still here?"
Davidson shrugged fractionally, his gaze steady on Garwood. "Not really. I believe Colonel Bidwell has been able to plug the hole you got out by the last time."
"I'm not surprised." The look in Davidson's eyes was becoming just the least bit unnerving. "May I ask why you're here, then?"