Harlan said, "What if I don't find it?"
"You will. Eternity exists, doesn't it. As long as it does, we're on the right track. Tell me, can you recall such an advertisement in your work with Cooper? Anything which struck you, even momentarily, as odd, queer, unusual, subtly wrong."
"No."
"I don't want an answer so quickly. Take five minutes and think."
"No point. At the time I was going over the news magazines with Cooper, he hadn't been in the 20th."
"Please, boy. Use your head. Sending Cooper to the 20th has introduced an alteration. There's no Change; it isn't an irreversible alteration. But there have been some changes with a small 'c,' or micro-changes, as it is usually referred to in Computation. At the instant Cooper was sent to the 20th, the advertisement appeared in the appropriate issue of the magazine. Your own Reality has micro-changed in the sense that you may have looked at the page with that advertisement on it rather than one without that advertisement as you did in the previous Reality. Do you understand?"
Harlan was again bewildered, almost as much at the ease with which Twissell picked his way through the jungle of temporal logic, as at the "paradoxes" of Time. He shook his head, "I remember nothing of the sort."
"Well, then, where do you keep the files of that periodical?"
"I had a special library built on Level Two, using the Cooper priority."
"Good enough," said Twissell. "Let's go there. Now!"
Harlan watched Twissell stare curiously at the old, bound volumes in the library and then take one down. They were so old that the fragile paper had to be preserved by special methods and they creaked under Twissell's insufficiently gentle handling.
Harlan winced. In better times he would have ordered Twissell away from the books, Senior Computer though he was.
The old man peered through the crinkling pages and silently mouthed the archaic words. "This is the English the linguists are always talking about, isn't it?" he asked, tapping a page.
"Yes. English," muttered Harlan.
Twissell put the volume back. "Heavy and clumsy."
Harlan shrugged. To be sure, most of the Centuries of Eternity were film eras. A respectable minority were molecular-recording eras. Still, print and paper were not unheard of.
He said, "Books don't require the investment in technology that films do."
Twissell rubbed his chin. "Quite. Shall we get started?"
He took another volume down from the shelf, opening it at random and staring at the page with odd intentness.
Harlan thought: Does the man think he's going to hit the solution by a lucky stab?
The thought might have been correct, for Twissell, meeting Harlan's appraising eyes, reddened and put the book back.
Harlan took the first volume of the 19.25th Centicentury and began turning the pages regularly. Only his right hand and his eyes moved. The rest of his body remained at rigid attention.
At what seemed aeonic intervals to himself Harlan rose, grunting, for a new volume. On those occasions there would be the coffee break or the sandwich break or the other breaks.
Harlan said heavily, "It's useless your staying."
Twissell said, "Do I bother you?"
"No."
"Then I'll stay," muttered Twissell. Throughout he wandered occasionally to the bookshelves, staring helplessly at the bindings. The sparks of his furious cigarettes burned his finger ends at times, but he disregarded them.
A physioday ended.
Sleep was poor and sparse. Midmorning, between two volumes, Twissell lingered over his last sip of coffee and said, "I wonder sometimes why I didn't throw up my Computership after the matter of my-- You know."
Harlan nodded.
"I felt like it," the old man went on. "I felt like it. For physiomonths, I hoped desperately that no Changes would come my way. I got morbid about it. I began to wonder if Changes were right. Funny, the tricks emotions will play on you.
"You know Primitive history, Harlan. You know what it was like. Its Reality flowed blindly along the line of maximum probability. If that maximum probability involved a pandemic, or ten Centuries of slave economy, a breakdown of technology, or even a-a-let's see, what's really bad-even an atomic war if one had been possible then, why, by Time, it happened. There was nothing to stop it.
"But where Eternity exists, that's been stopped. Upwhen from the 28th, things like that don't happen. Father Time, we've lifted our Reality to a level of well-being far beyond anything Primitive times could imagine; to a level which, but for the interference of Eternity, would have been very low probability indeed."
Harlan thought in shame: What's he trying to do? Get me to work harder? I'm doing my best.
Twissell said, "If we miss our chance now, Eternity disappears, probably through all of physiotime. And in one vast Change all Reality reverts to maximum probability with, I am positive, atomic warfare and the end of man."
Harlan said, "I'd better get on to the next volume."
At the next break Twissell said helplessly, "There's so much to do. Isn't there a faster way?"
Harlan said, "Name it. To me it seems that I must look at every single page. And look at every part of it, too. How can I do it faster?"
Methodically he turned the pages.
"Eventually," said Harlan, "the print starts blurring and that means it's time for sleep."
A second physioday ended.
At 10:22 A.M., Standard Physiotime, of the third physioday of the search Harlan stared at a page in quiet wonder and said, "This is it!"
Twissell didn't absorb the statement. He said, "What?"
Harlan looked up, his face twisted with astonishment. "You know, I didn't believe it. By Time, I never really believed it, even while you were working out all that rigmarole about news magazines and advertisements."
Twissell had absorbed it now. "_You've found it!_"
He leaped at the volume Harlan was holding, clutching at it with shaking fingers.
Harlan held it out of reach and slammed the volume shut. "Just a moment. You won't find it, even if I showed you the page."
"What are you doing?" shrieked Twissell. "You've lost it."
"It's not lost. I know where it is. But first--"
"First what?"
Harlan said, "There's one point remaining, Computer Twissell. You say I can have Noys. Bring her to me, then. Let me see her."
Twissell stared at Harlan, his thin white hair in disarray. "Are you joking?"
"No," said Harlan sharply, "I'm not joking. You assured me that you would make arrangments- Are you joking? Noys and I would be together. You promised that."
"Yes, I did. That part's settled."
"Then produce her alive, well, and untouched."
"But I don't understand you. I don't have her. No one has. She's still in the far upwhen, where Finge reported her to be. No one has touched her. Great Time, I told you she was safe."
Harlan stared at the old man and grew tense. He said, chokingly, "You're playing with words. All right, she's in the far upwhen, but what good is that to me? Take down the barrier at the 100,000th-"
"The what?"
"The barrier. The kettle won't pass it."
"You never said anything of this," said Twissell wildly.
"I haven't?" said Harlan with sharp surprise. Hadn't he? He had thought of it often enough. Had he never said a word about it? He couldn't recall, at that. But then he hardened.