“Which are?”

“Ionizing radiation coming from outer space. A stream of protons, helium nuclei, and other nuclei. When they collide with nuclei in our atmosphere, they produce secondary radiation—mostly pions, muons, electrons, and dutar rays.”

“And these are dangerous?”

“Not really—at least, not in the small quantities produced by cosmic rays. But they do interfere with delicate instruments, and so we wanted to set up our equipment somewhere that was shielded from them. And, well, the Debral nickel mine was nearby.”

“Couldn’t you have used another facility?”

“Conceivably, I suppose. But Debral is unique not only for its depth—it is the deepest mine in the world—but also for the low background radiation of its rocks. The uranium and other radioactives present in many other mines give off charged particles that would have impaired our instruments.”

“So you were well shielded down there?”

“Yes—from everything except neutrinos, I suppose.” Adikor caught the expression on Adjudicator Sard’s face. “Minuscule particles that stream right through solid matter; nothing can shield against them.”

“Now, weren’t you also shielded against something else down there?” asked Bolbay.

“I don’t understand,” said Adikor

“A thousand armspans of rock between you and the surface. No radiation—not even cosmic-ray particles that had traveled unimpeded for huge distances—could get down to you.”

“Correct.”

“And no radiation could make it up from the surface to where you were working, isn’t that right?”

“How do you mean?”

“I mean,” said Bolbay, “that the signals from your Companions—yours, and Scholar Boddit’s—could not be transmitted out of there to the surface.”

“Yes, that’s true, although I hadn’t really given it any thought until an enforcer mentioned it to me yesterday.”

“Hadn’t given it much thought?” Bolbay’s tone was one of incredulity. “Since the day you were born, you’ve had a personal recording cube in the alibi-archive pavilion adjacent to this very Council building. And it has recorded everything you’ve done, every moment of your life, as transmitted by your Companion. Every moment of your life, that is, except the time you spent far, far below Earth’s surface.”

“I’m no expert on such matters,” said Adikor, somewhat disingenuously. “I really don’t know much about the transmission of data from a Companion.”

“Come now, Scholar Huld. A moment ago you were regaling us with stories of muons and pions, and now you expect us to believe you don’t understand simple radio broadcasting?”

“I didn’t say I don’t understand it,” said Adikor. “It’s just that I’ve never thought about the issue that’s been raised.”

Bolbay was behind him again. “Never thought about the fact, that, while down there, for the first time since your birth, there would be no record available of what you were doing?”

“Look,” said Adikor, speaking directly to the adjudicator, before the orbiting Bolbay blocked his line of sight again. “I haven’t had cause to access my own alibi archive for countless months. Sure, the fact that my actions are normally being recorded is something I’m aware of, in an abstract sense, but I just don’t think about it every day.”

“And yet,” said Bolbay, “every day of your life, you enjoy the peace and safety made possible by that very recording.” She looked at the adjudicator. “You know that as you walk at night, the chances of you being the victim of robbery or murder or lasagklat are almost zero, because there’s no way to get away with such a crime. If you charged that—well, say, that I had attacked you in Peslar Square, and you could convince an adjudicator that your charge was reasonable, the adjudicator could order your alibi archive or mine unlocked for the time span in question, which would prove that I am innocent. But the fact that a crime cannot be committed without a record of it being made lets us all relax.”

Adikor said nothing.

“Except,” said Bolbay, “when someone contrives a situation to secrete himself and his victim in a place—practically the only place—in which no record of what happens between them could have been made.”

“That’s preposterous,” said Adikor.

“Is it? The mine was dug long before the beginning of the Companion Era, and, of course, we’ve used robots to do the mining for ages now. It’s almost unheard of for a human to have to go down into that mine, which is why we’ve never addressed the problem of lack of communication between Companions there and the alibi-archive pavilion. But you set up a situation in which you and Scholar Boddit would be in this subterranean hideaway for great spans of time.”

“We didn’t even think about that.”

“No?” said Bolbay. “Do you recognize the name Kobast Gant?”

Adikor’s heart pounded, and his mouth went dry. “He’s an artificial-intelligence researcher.”

“Indeed he is. And he will state that seven months ago he upgraded both your Companion and Scholar Boddit’s, adding sophisticated artificial-intelligence components to them.”

“Yes,” said Adikor. “He did that.”

“Why?”

“Well, um …”

“Why?”

“Because Ponter hadn’t liked being out of touch with the planetary information network. With our Companions cut off from the network down there, he thought it would be handy to have a lot more processing power localized in them, so that they could help us more with our work.”

“And you somehow forgot this?” said Bolbay.

“As you said,” replied Adikor, his tone sharp, “it was done months ago. I’d gotten quite used to having a Companion that was more chatty than usual. After all, I’m sure Kobast Gant will also state that, although these were early versions of his companionable artificial-intelligence software, his intention was to make it available for all those who wanted it. He expected people to find it quite helpful, even if they are never cut off from the network—and he felt people would get used to it quickly, so that it would soon be as natural to them as having a dumber Companion.” Adikor folded his hands in his lap. “Well, I rapidly got used to mine, and, as I said at the outset, I didn’t give much thought to it, or to why it had originally been necessary … but … wait! Wait!”

“Yes?” said Bolbay.

Adikor looked directly at Adjudicator Sard, seated across the room. “My Companion could tell you what happened down there!”

The adjudicator leveled a steady stare at Adikor. “What is your contribution, Scholar Huld?” she asked.

“Me? I’m a physicist.”

“And a computer programmer, is that not so?” said the adjudicator. “Indeed, you and Scholar Boddit were working on complex computers.”

“Yes, but—”

“So,” said the adjudicator, “I hardly think we can trust anything your Companion might say. It would be a trivial enough matter for one of your expertise to program it to tell us whatever you wanted it to.”

“But I—”

“Thank you, Adjudicator Sard,” said Bolbay. “Now, tell us, Scholar Huld, how many people are normally involved in a scientific experiment?”

“That’s a meaningless question,” said Adikor. “Some projects are undertaken by a single individual, and—”

“—and some are undertaken by tens of researchers, isn’t that true?”

“Sometimes, yes.”

“But your experiment involved just two researchers.”

“That’s not correct,” said Adikor. “Four other people worked on various stages of our project.”

“But none of them were invited down into the mine-shaft. Only the two of you—Ponter Boddit and Adikor Huld—went down there, isn’t that right?”

Adikor nodded.

“And only one of you returned to the surface.”

Adikor was impassive.

“Isn’t that right, Scholar Huld? Only one of you returned to the surface.”

“Yes,” he said, “but, as I’ve explained, Scholar Boddit disappeared.”

“Disappeared,” said Bolbay, as if she’d never heard the word before, as if she were struggling to comprehend its meaning. “You mean he vanished?”