Ponter replied, “Dusble korbul to kalbtadu.” And the implant, using its male voice, provided the translation: “In a quantum-computing facility.”

“Quantum computing?” repeated Mary, but feeling uncomfortable doing so; she wasn’t used to being the most ignorant one in the room.

“That’s right,” said Reuben, grinning. “Dr. Benoit?”

Louise got up and nodded at the M.D. “Quantum computing is something we’re just starting to play with ourselves,” she said, pushing hair out of her eyes. “A regular computer can determine the factors of a given number by trying one possible factor to see if it works, then another, then another, then another: brute-force calculation. But if you used a conventional computer to factor a big number—say, one with 512 digits, like those used to encrypt credit-card transactions on the World Wide Web—it would take countless centuries to try all the possible factors one at a time.”

She, too, looked from face to face, making sure she hadn’t lost her audience. “But a quantum computer uses superposition of quantum states to check multiple possible factors simultaneously,” said Louise. “That is, in essence, new short-lived duplicate universes are spun off specifically to do the quantum calculation, and, once the factoring is complete—which would be virtually instantaneously—all those universes collapse back down into one again, since, except for the candidate number they tested to see if it was a factor, they’re otherwise identical. And so, in the time it takes to try just one factor, you actually get them all tried simultaneously, and you solve a previously intractable problem.” She paused. “At least, until now, that’s how we’ve believed quantum computing works—relying on the momentary superposition of quantum states effectively creating different universes.”

Mary nodded, trying to follow along.

“But suppose that isn’t how it really happens,” said Louise. “Suppose that rather than creating temporary universes for a fraction of a second, a quantum computer instead accesses already existing parallel universes—other versions of reality in which the quantum computer also exists.”

“There’s no theoretical basis for believing that,” said Bonnie Jean, sounding annoyed. “And, besides, there’s no quantum computer at this location, in the only universe that we know does exist.”

“Exactly!” said Louise. “What I propose is this: Dr. Boddit and his colleague were trying to factor a number so large that to check every possible factor of it required more versions of the quantum computer than there were in separate already existing long-term universes. Do you see? It reached into thousands—millions!—of existing ones. And in each of those parallel universes, the quantum computer found a duplicate of itself, and that duplicate tried a different potential factor. Right? But what if you were factoring a huge number, a gigantic number, a number with more possible factors than there are parallel universes in which the quantum-computing facility already exists? What then? Well, I think that’s what happened here: Dr. Boddit and his partner were factoring a gigantic number, the quantum computer found its siblings in all—every single one—of the parallel universes in which it already existed, but it still needed more copies of itself, and so it went looking in other parallel universes, including ones in which the quantum-computing facility had never been built—such as our universe. And when it reached one of those, it was like hitting a wall, causing the factoring experiment to abort. And that crash caused a large part of Ponter’s computing facility to be transferred into this universe.”

Mary noted that Dr. Mah was nodding. “The air that accompanied Ponter.”

“Exactly,” said Louise. “As we’d guessed, it was mostly just air transferred to this universe—enough air to burst open the acrylic sphere. But, in addition to the air, one person, who happened to be standing in the quantum-computing facility, was transferred, as well.”

“So he didn’t know he was going to come here?” asked Mah.

“No,” said Reuben Montego, “he didn’t. If you think we were shocked, imagine how shocked he was. The poor guy instantly found himself submerged in water, in absolute darkness. If there hadn’t been that massive bubble of air transferred with him, he would have drowned for sure.”

Your whole world turned inside out, thought Mary. She looked at the Neanderthal. He was certainly doing a good job of hiding the disorientation and fear he must feel, but the shock surely had been enormous.

Mary gave him a small, empathetic smile.

Adikor Huld’s dooslarm basadlarm continued. Adjudicator Sard still sat at the south end, and Adikor remained in the hot seat, with Daklar Bolbay stalking around him in circles.

“Has a crime really been committed?” asked Bolbay, looking now at Adjudicator Sard. “No dead body has been found, and so one might argue that this is simply a case of a missing individual, no matter how improbable such a circumstance seems today. But we have searched the mine with portable signal detectors, and so we know that Ponter’s implant is not transmitting. If he were injured, it would be transmitting. Even if he were dead by natural causes, it would continue to transmit, using stored power, for days after Ponter’s own biochemical processes ceased. Nothing short of violent action can account for the disappearance of Ponter and the silence of his Companion.”

Adikor felt his stomach knotting. Bolbay was right, as far as her reasoning went: the Companions were designed to be foolproof. Before they existed, people did sometimes just go missing, and only after many months were they declared dead, usually simply for lack of a better explanation. But Lonwis Trob had promised his Companions would change that, and they had. No one just disappeared anymore.

Sard obviously agreed. “I’m satisfied,” she said, “that the lack both of a body and of Companion transmissions suggests criminal activity. Let’s get on with it.”

“Very well,” said Bolbay. She looked briefly at Adikor, then turned back to the adjudicator. “Murder,” Bolbay said, “has never been common. To end the life of another—to put a complete and utter stop to someone’s existence—is heinous beyond compare. But, still, there are cases known, most, I grant you, from before the time of the Companions and the alibi-archive recorders. And in previous cases, the tribunals asked for three things to be shown to support a charge of murder.

“The first is a chance to commit the crime—and this Adikor Huld had in a way that no one else on this planet did, for he was beyond the capabilities of his Companion to transmit his actions.

“The second is a technique, a way in which the crime might have been committed. Without a body, we can only speculate on how it might have been done, although, as you will see later, one method is particularly likely.

“And, finally, one needs to show a reason, a rationale for the crime, something that would cause one to commit so awful, so permanent an act. And it’s that question of reason I’d like to explore now, Adjudicator.”

The old female nodded. “I’m listening.”

Bolbay swung to face Adikor. “You and Ponter Boddit lived together, isn’t that true?”

Adikor nodded. “For six tenmonths.”

“Did you love him?”

“Yes. Very much indeed.”

“But his woman-mate had died recently.”

“She was also your woman-mate,” said Adikor, taking the opportunity to emphasize Bolbay’s conflict of interest.

But Bolbay was up to the occasion. “Yes. Klast, my beloved. She is no longer alive, and for that I feel great sorrow. But I blame no one; there is no one to blame. Illness happens, and the life-prolongers did all they could to make her final months comfortable. But for the death of Ponter Boddit, there is someone to blame.”