Grey has just put the last of the pieces together in his head when he hears the first scream from outside the shaft. The timing is uncanny. He has spent a week and a half taking photographs and drawing schematics and dispatching hesitant mana pings into likely-looking receptors in the surface of the artifact. He has observed the series of inexplicable and then unnerving and then mind-wrenching real-world effects of powering the thing up. He has spent that time patiently avoiding leaping to the conclusion. He has tested every step and ruled out every alternative. And he has, after ten-and-a-half days, for one moment, permitted himself to entertain the possibility that what he's looking at is what he feared at first glance he was looking at, and at that instant he hears what sounds like the world above being Cleaned, and it's almost a relief.

Magic is a science. It's a science as advanced as any other, as quantum field theory or general relativity, and there have been outlandish claims and vague or self-fulfilling prophecies and forged or questionable evidence, but there is no concrete evidence, none, that anybody knew anything about it until Suravaram Vidyasagar cast uum for the first time in 1972. There were no ancient astronauts. There were no real witches at Salem. Jesus wasn't a mage-- nothing that he or Muhammed or the Buddha are ever claimed to have done matches up with modern magic. Artifacts from the pre-magic era are one hundred percent non-magical; magical artifacts "from that era" are one hundred percent forged. And the reason for this, which most of the world accepts, is that magic wasn't in reach then. Nobody had the knowledge of physics that was necessary, because the physics that was necessary hadn't been discovered and locked down yet. It was luck, arguably dumb: magic could have been discovered decades earlier or, equally, could have remained unknown long past the present day.

But the artifact that Gareth Grey's high-altitude thaumomagnetic survey found in the far east of the DRC, which it's taken his expedition a month to reach and dig down to, could turn all of that on its ear. It's the rabbit in the Cretaceous, the Casio wristwatch in the coal seam. It's a magic ring as big as a Stonehenge megalith, and it's embedded in rock fifty million years earlier than it could ever exist. There have been geological explanations suggested for its position, but they aren't convincing. And there's certainly no theory in the whole of human knowledge for who could have made it. It can't exist. It's beyond inexplicable. It represents a discontinuity in Grey's rational universe, a false statement which, thanks to the principle of explosion, logically implies the destruction of all reasoned thought. All statements are now false and true.

Aliens. Time travel. A practical joke?

But the thing is huge. Magic rings in modern engineering are of course as big as they need to be: at CERN Grey saw one wide enough to fly a light aircraft through the middle. But no magic ring is this fat and surely no practical magic ring weighs this much. Based on the geophysical scan (most of the object is still buried) it's thirteen metres wide and two thick, with the cylindrical hole through the middle just a metre and a half wide. If the thing's solid metal, it could weigh anything up to four thousand tonnes - assuming the metal can be identified. It could be moved. It would take an army, but it could be moved. An army isn't out of the question. An army could use it. More efficiently than anybody, in fact, Grey thinks.

The metal is shiny and silvery which rules out, oh, copper and osmium and precious little else. Except for a small, faint etched plus sign, it's smooth all over the exterior and the flat top face (again, as far as they've excavated). About forty percent of the cylindrical hole's inner surface has been uncovered. Into the inner rim, big, bold sigils are etched and there are more, smaller sigils etched into surface of those sigils, and a third iteration etched into those in turn. The writing is so dense and sharp as to be incoherent; regardless of how well-preserved the metalwork seems to be, uncovering enough of it to activate the ring has been painstaking. Grey feels dwarfed by its complexity. Way back in the Stone Age of computing, when the available resources meant that programs had to be minuscule and neatly folded and unreadably, irreducibly complex just to fit, let alone run, this is the kind of code that Grey saw and wrote. These sigils are at the same density and at the same degree of interconnectedness. Inadvisably tightly coupled and organic.

That's the word Grey is afraid of, "organic". If the artifact was grown and machined by some thrashing, senseless neural net, this is what you'd see. If the problem the thing was designed to solve was so complex that the solution wouldn't be recognisably designed at all, this is what you'd see. When he powers it up, Grey feels like an ant trying to understand the console of the starship Enterprise. And when he powers it up, it still, after N years, works.

The first time he put a jolt through it, a few insect bites disappeared from his arm. It was a whole day before he noticed.

There are more screams. The excavated shaft is a steep diagonal corridor cut into the side of a thickly rainforested mountain. The first part was easy, a thin upper layer of poor soil (as red as Mars and about as fertile), dry leaves and ants. After that it was a dangerously dusty, noisy, mechanical job using heavy machinery which was badly-maintained to start with and which had become visibly even worse for wear on the journey into the Congolese interior. The shaft is about fifteen metres long, with plenty of head room, but barely wide enough for one person to slide past another. The chamber at the bottom where the ring is being excavated is a little bigger, with room for a proper light and a camping chair. Given another month without interruptions, Grey would have had the whole roof pulled off, exposing the ring to fresh air for the first time in - depending on your hypothesis - tens, hundreds, thousands or millions of years. But Grey made them cut to the core directly. He wanted to see it. And that means he's trapped alone at the bottom of a hellishly hot, lung-scratchingly dusty hole in the ground, with no weapons beside an archaeologist's brush, a face mask and a mattock.

He blames himself for calling attention. He could have dropped the matter, let the odd readings stay odd and unseen forever and continued charting the grander topology of low-grade natural background magic on the African continent. But he wanted to see something that nobody else had ever seen before. He wanted to find buried treasure.

Grey stares up the shaft for a long moment, squinting at the light, waiting for somebody to appear at the mouth. They're here for the ring. There's no other conceivable reason for anybody to be this far into the rainforest. Which means it's as valuable as he fears.

There are two more shouts and the sound of running and the sound of bodies falling. There's no gunfire, though. He looks down at the walkie-talkie in the dust and considers trying to contact somebody up above for help, perhaps to organise a distraction. But then he counts up the screams he's heard-- there can only be at most one or two of the expedition left, and they'll be running for their lives. The noise from a crackling walkie-talkie could give them away. Could he wait until dark? If he switched off the lamp down here, could he jump whoever came down to investigate? He hefts the mattock in one hand. It's balanced all wrong for use as a weapon; he'd knock holes in his own limbs by accident. Maybe he could throw the mattock out of the shaft, so that it would land elsewhere, distracting whoever is out there for long enough for him to make a run for the Jeep. How many people are out there, anyway? Surely no more than four or five. Otherwise the whole camp would have been swamped in seconds, not minutes.

Possibilities tumble. Having convinced himself that there's no way out of the situation alive, Grey wonders if he can still win by bringing the shaft down on his own head, or by destroying the artifact. But he oversaw the beaming and propping too carefully for the former to be an option, and as for the latter... it's a four-thousand-tonne doughnut of metal. As delicate as its engravings are, he'd need strong acid to do anything worse than a slight dent.

And having come to the end of that thread, having realised that he's not just dead but beaten, he remembers how far he is from home.

He exhales hard and clenches his teeth. "Damn."

"Penny for your thoughts, Dr. Grey," says a voice. At the mouth of the shaft, Grey sees the silhouette of a bald man in a dark, loose-cut suit. The man has no visible weapon. He holds onto the roof of the entrance for support, for a casual effect.

"How many of my people have you killed?" Grey demands.

"The four drivers. The two engineers. The guide and his brother. The blonde geologist and the dark-haired geologist she liked. And the fellow who carried your amulets. That's everybody." The faceless man states it as fact.

"That's everybody," agrees Grey. He hurls the mattock overarm, as hard as he can. The trajectory is long and flat enough to avoid the ceiling and walls of the shaft. Then there's a smash cut. Subjective time skips.

He's--

--flat on his back, waking up. His head is as clear as a bell. He's an early bird, but as far back as he can remember he's never woken up so cleanly, with so much clarity. Certainly not after being knocked unconscious. He detects no head injury. Gas? He sits up in the mud and squints at the light. He's still in the shaft, lying with his head and upper body in the partially excavated doughnut hole, and it's still daylight outside.

The mud, he discovers when he brushes it from his hands and hair, isn't wet dirt. It's gore. Grey recognises brain matter and chunks of skull. The other half of the doughnut hole, which is still plugged up with stone, is splattered with an entire head full of blood.

Well. That answers some questions.

Earlier, tentative experimentation had shown that the machine could resolve cuts and scars and, in one of the engineers, a years-old mild limp of uncertain origin. It was also shown to restore eyesight, which Grey found moderately troublesome, since his only sunglasses were prescription. But that was the limit. There was no chance that he was going to ask somebody, in a spirit of scientific inquiry, to deliberately break a bone and see if the machine could fix it. That would have been madness. He stands by the decision, even now, standing in the splatter pattern of his own detonated head.

So it can fix brains, from a standing start. Presumably he had to be nearby for it to record a pattern to work from. It would be impossible, surely, to put a human mind back together properly without some kind of "known-good" template to work from...

Grey cackles. "Impossible".

He thinks back to the smash cut and wonders how he'd detect other inconsistencies in his own memories under these circumstances. Did the machine restore his mind fully, or partially? There are other questions still open: can it do anything about mental illness? What about extreme age? What about non-humans?

There's no bullet or hole. He doesn't remember a gunshot. Not even a silenced round. Not even a weapon being raised.

He climbs to the mouth of the shaft and pokes his head out, blinking. The sunlight is so bright that it feels as if it has physical weight. Below the shaft mouth is the wide, mucky orange path that leads down to the camp site, a wide clearing littered with tents, parked vehicles and diesel generators. From where he's standing, Grey counts seven corpses. The bullet wounds that he can see look like clean chest shots. But he can't see the man. He can't see anybody living.

Quietly and with extreme caution, he sidles down towards the camp, through the trees rather than down the obvious path. If he can reach his tent, he can unlock the small metal trunk and reassemble his rifle. Then he can use it to keep his nerves subdued while he works out a plan.

"I said, what do you think?" asks the same voice, this time from behind. Grey sags, the effort of stealth wasted. He turns. The bald man is emerging from the same excavated shaft, which should be empty, but Grey is too tired to absorb this extra oddity. The man's tall and very young. Closer to a boy, in fact. Early twenties at the latest. He's young and he stands casually, with his hands in his pockets. His linen suit is loose and its jacket is unbuttoned: Grey sees no gun. He looks around and still sees no accomplices.

"You can have it," says Grey. "I don't care what you do with it. Just give me enough time to use it to bring my people back."

The youth smiles faintly and shakes his head.

Grey conceals his anger. He decides to play the boy's game, to buy time. "It's obviously a doctor. I suspected from the Red Cross symbol on its hull. It's the mechanical realisation of the abstract concept: a machine which makes people better. The most complicated medical device ever created, a million times more complicated than any medical device I've ever seen and a thousand times more complicated than the human body it's designed to fix. And... it can't exist. I can't even conceive of magic so advanced. No human can, no matter the IQ. It can't exist. I'm a mage and I know magic isn't like this."

"But what do you think?"

"What do I think about what?"

"What do you think happens next?"

"Obviously you and whoever else is with you are going to kill me and take the machine."

"What if I didn't do that?"

Grey blinks. "...We would need to get it to a laboratory," he says. "Because one isn't enough. If we put the thing at the most accessible point on Earth and formed a human processing system ten times as complicated as Mecca, and forced people through the machine one at a time, one every two seconds, for the rest of time, it wouldn't be enough. It wouldn't register statistically. It wouldn't make a dent in any of the rates. Which means we need to make more. Millions more. This is... it's Outside Context Medicine."

"And then what would happen?"

Grey stares into a distant possible future. "Medicine as we know it would-- it would become magic. Everything we know about medicine would be revolutionised. We'd write libraries about what the machine does to people, the difference between broken and fixed people. And then we would throw away those libraries because we'd never need them again because everybody would live to a hundred and twenty without trying. If you lived inside a machine you could live for eternity. And if there's a way that the machine can reverse telomere shortening, then everybody on Earth could live forever just with periodic visits. You could have eternal youth. For everybody."

"And then what?"

"And then?" Grey concentrates. "There would-- there would be no Malthusian catastrophe. There wouldn't need to be. Because you don't need food and water anymore. You visit the machine. Malnourished? Visit the machine. You come out the other side fed and watered. Food becomes a luxury item. The capacity of the planet becomes a function of physical space. Maybe if the technology can be adapted, the whole of the world could be pervaded with this restorative power. You wouldn't need to eat, or drink. Or even breathe. You wouldn't need air anymore. You'd-- You'd have to rediscover death."

The bald youth reflects for a long moment, and then asks, "A likely story, do you think?"

Grey smiles darkly. "Of course not. None of it."

The youth says, "Here's what we think: A major medical research company pays for the rights to study, own and operate the machine. At great length and expense, they duplicate it. They want a return on their investment. They make eight machines, embed them in purpose-built medical establishments in world cities and sell the best medical care that is theoretically possible to only those able to afford millions of U.S. dollars per visit. When it becomes clear what the organisation is sitting on, it becomes the target of heavyweight litigation, industrial espionage and eventually overt physical attacks. A man is denied access due to perceived war crimes; another man, also a perceived war criminal, is admitted. Unrelated tensions boil over at the same time, amplifying the situation. A full European War erupts.

"But in fact, what's more likely is that the machine proves unduplicable. Its location on neutral territory in, for example, the Hague, the Netherlands, becomes the nucleus of a community of ill and dying pilgrims desperately queueing for one-time exposure to a machine which cannot physically process one in a hundred of the patients who need its treatment. A second city is founded on the streets of the first. First crime consumes both cities, then disease, then violence. In the final series of riots, the facility is stormed and the machine captured by a dozen different groups in a single week. Eventually the Dutch military end the conflict by permanently disabling the machine.

"But even that's an outside chance because, in the first place, you're never likely to get it out of the DRC unchallenged. Eight African nations including the Democratic Republic of the Congo itself become aware of the machine's existence and initiate a decades-long, interminable land war to claim it. Western nations become involved and the war in turn claims millions of lives and ends with the tactical atomic bombing by the United States of the installation where the machine is being held. Even though the machine was believed to have been rendered unrecoverably inoperable years earlier, the bombing is regarded as the greatest humanitarian catastrophe of all time.

"Except that that might not happen either. Let's say the U.S. wins the war. They capture the machine and take to the bunker underneath the White House, where only the President, his family and his cabinet are permitted access to it. Medical technology is deliberately stalled and never reaches the pinnacle it should.

"And yet, for anybody to leave the machine unexploited is implausible. We spin more numbers and simulations and we see the machine being reverse-engineered, and the principles it applies being adapted for purposes other than the immediate, perfect restoration of living and dead humans. Mr Grey, you've seen how easy it is to heal. Can you imagine how easy it'll become to kill?

"The truth will inevitably be somewhere in the middle of all of these possibilities, but I'm sure you understand the common theme. Death surrounds this machine, like a curse. Death and leverage. The mother of all MacGuffins."

Grey imagines how easy it would become to kill. You wouldn't need a gun anymore. You could create a bullet and give it motion. You could simply "correct" a living human body to a living body with a hole in it.

"And you see," the youth concludes, "that you have to let us take it and put it somewhere safer."

"Take it back, you mean," Grey says.

"...Indeed."

"It must have been in a hell of an accident to wind up inside a mountain," Grey says. "How did you lose it?"

The young man shrugs.

"But how did you know we'd found it? I chose my crew for loyalty. Until yesterday, I didn't utter a hint to them about what I thought the thing actually was. And I know none of them satphoned home."

"Magic."

"Then who are you?"

"I can't tell you."

"But you're going to kill me."

In response, the youth nods towards the shaft mouth. "It's still a risk. You understand."

Grey does.

The youth continues, "All I can say is that we're the ones who ran the numbers. Of course, nobody can accurately predict the future, but after ten thousand high-fidelity simulations of the same events, some outcomes turn out to be more probable than others, and then when we go through our courses of action, this is the firmest recommendation."

Grey's eyes widen. He puts his hands out, mind racing, heart racing. "Wait. No, wait!"

The youth pulls his right hand out of his pocket and says "One more, please," seemingly to nobody before pointing at Grey with his first two fingers.

"How good are your simulations? What kind of fidelity? Was I a component? Could you be?" Grey delivers all four questions in about three seconds.

There's a pause. The boy doesn't lower his hand, but Grey's got his attention.

"How would the simulation begin?" Grey continues. "If you were simulating this course of action, how would it begin? It would begin with the decision being made, right?"

A longer pause.

Grey says, "It would begin exactly like this. No matter the option, no matter the outcome. The course of action to be tested is X . So they create a simulation in which the course of action selected was X . In the simulation, you are given the order. In the simulation, a simulation of you carries X out. And as it plays out, the simulators observe the results. They collect the results from X and Y and Z and stack them all together. And then pick the best one and they go out into reality and do it once, for real.

"Think about it. You, you, know all of the possible outcomes if nobody does anything, if nobody interferes," Grey says. "Because those runs were run. But you don't know what the other options of interference are. You don't know about the other hypotheses. About Y and Z and the rest. That's the only way that you could prove that this isn't a hypothetical, because that information is the only information that's guaranteed not to be available inside a hypothetical. And you don't have it. And this can't be the right solution because it doesn't make sense. Killing to prevent more killing? Killing to prevent a medical revolution that could save literally every life? This has to be one of the faulty hypotheses. And that means that you and I don't exist. This isn't happening. So it doesn't matter if you don't kill me."

"Then it doesn't matter if I do--"

"But the point is that X doesn't have to happen here. Make this the one where you gained unexpected self-awareness and disobeyed orders. Put your... absence of gun away. Maybe that's what they really want to see happen. They order you to do X but they want me to overrule you with Y so they can see how Y plays out. They want to see what happens if... you let me try to save everyone." Grey locks eye contact with the youth. Grey tries to make himself believe that he sees a flicker of doubt in there.

There is the longest pause.

"No," says the boy. "This is real."

He shoots Grey. No gun. No bullet. He just opens a hole in Grey's heart.