"Did you say Natalie Ferno?"

Exa just took a mobile phone call while travelling through the Channel Tunnel. This is a completely normal thing that he can do. He was bound for the bomb site already, but the specific task of interrogating this one woman has only just arrived.

"Affirma--"

"Natalie Ferno?"

"Affirmative," Casaccia repeats. "Problem?"

"Check your files," Exa says.

"Hmm?"

"We have history with that woman. Four years ago. I don't blame you for trying to forget about it. Look her up, do it now. The relevant keyword is 'fiasco'."

Casaccia does so. Some seconds elapse as he reads. His eventual response is a long inhalation followed by a single, drawn-out swear word.

Exa sighs. He sometimes thinks he's the only competent person in the entire organisation.

*

Zeck's been called Zeck for so long that it even appears on official University documentation. Sometimes people who don't know him well try to call him by his birth name, but it always comes off as slightly insulting, not just because they inevitably mangle it, but because "Zeck" is, according to everybody including Zeck, the man's real name.

Zeck's wife calls him Zeck.

Their house is built wholly from flat surfaces: windowsills, mantlepieces, side tables, nooks. Every flat surface is covered with greying knick-knacks. The place would be a nightmare to dust if either of them dusted it. Zeck is old and immobile enough that he's one of the few theoretical magic tutors to host tutorial sessions at his own home. He and Natalie usually work at the kitchen table, which, while it is as cluttered with objects as any other flat surface in the house, is at least cluttered with objects which can be picked up and piled up elsewhere.

Zeck is a perfectly cordial human being, and a fine tutor. His house makes Nat's skin crawl. It's a cold place, too. It rattles in the wind.

It's the first term of Nat's first undergraduate year. Zeck tutors Phonic Algebra. Out of all of introductory theoretical magic, Phonic Algebra is the course which would be the least recognisable to students of, say, physics. Magic has a language: an alphabet, a vocabulary, a grammar and an accent. Everything a mage says means something. Every syllable does something to the preceding syllables and to the universe. The topic is "basic", in that it forms the basis for almost all magical theory, but it is also riddled with traps, one-time exceptions and maddeningly finely-distinguished vowel sounds.

It is extremely easy to write down spells which work perfectly on paper and which no human tongue can possibly pronounce.

Another fun fact: in 1978, a long but startlingly elegant theorem by Shilmani proved that the language of magic had a name. That is, that the language of magic contained within itself a name for the language of magic. The proof was not constructive; it was only in 1980 that Shilmani went on to prove that the name of the language of magic was, in fact, the empty string.

Point being, magic is so complicated as to be embarrassing, and protecting wannabe mages from that complexity is a great way to protect them from becoming mages. Phonic Algebra is the sharp end of the intro. It is the mandatory course which turns wannabe mages into either serious mages-in-training or equally serious electrical engineers.

"You did something interesting," Zeck says, beginning the session. He is reviewing Natalie's solutions to problems set the previous week. "Question ten. You solved it and then you overshot a little."

"What? Ah."

"Would you want to explain? You overflowed onto a whole back page of extra working. I'm not complaining, it's just that there aren't any extra marks back there."

"Does it make sense?"

"It does," Zeck says, nodding many times. "Where did it come from?"

Ultimately, it came from her mother. It was a curious and abstract result which, for Natalie, had existed in complete vacuum, memorable and yet pointless. It had never made sense to her until she saw question ten. And then it had been like applying voltage to a tangle of dull glass, and seeing the neon colours light up inside it.

But Natalie automatically withholds the whole truth.

"It just... worked."

Zeck says, "You got the question correct. That's fine, we don't need to belabour that. The 'extra credit' is correct as well. Except that this is a quite novel result. I haven't seen it before. Now--"

Zeck is old enough to predate magical science. Mages can be broadly broken down into two categories: those under forty, who essentially grew up inside magic, and those over forty, who retrained from some other discipline, and had to retrain hard to hold their own. Zeck was a respectable applied mathematician when upstart magic began muscling in on the research funding. He has seen magic unfold, live. He was one of the few people on Earth - other than the very earliest pioneers, the Vidyasagar enclave - to know, at one moment in time, all of the magic that was known by anyone at that time. That moment is a decade and a half in the past now, but the point still stands that if Zeck hasn't seen something before, there's a bankable probability that nobody has seen it before.

"--that's not to say it's going to shatter the Earth. It could be worth pursuing formally. Academically. Although it could equally be a little early for you, career-wise. Before we embark on that particular ship, I need to ask you again, are you sure this isn't derived from anywhere? Extracurricular reading?"

"No," Natalie lies.

"Then I think I might try it out," Zeck announces. Although specialising in theory, Natalie has been required to take a fixed quantity of practical courses. That means she's bound herself a True Name - once, with help - and can confidently get as far as eset , which is the magical equivalent of Chopsticks. Zeck is better-positioned to try a real spell out, although it would still be a break from habit. "It'll take some time to glom it together into a real spell, but I shall see whether I can find the time."

"That's, ah. Thank you. I didn't think it was important."

"It may not be! But, regardless, it's novel. We'll find out, if I can find the time," Zeck says. "Actually, what I shall do first is read around the subject a little and see whether I can't see whether it's been done. But, otherwise. If. Et cetera. So. No problems with questions one to nine. Ten is correct. Eleven is where you started to hit problems..."

This is Zeck and Natalie's second-to-last tutorial session of the academic term.

Their final session is a week later. Both of them have forgotten about the earlier discussion.

(Well, actually, Zeck has indeed tried the spell out, but the effects were forgettable. So, he decides not to mention it, unless Natalie raises the topic. Natalie correctly infers Zeck's line of reasoning, and does not mention it either. But it's the same thing in the end.)

After that, Phonic Algebra is over. Christmas is next, and in the spring, Natalie will move on to a whole new collection of courses and tutors.

Over Christmas, Natalie's near-identical twin sister is stabbed in the kidney by a man whom she (the sister) then kills in self-defence.

*

Exa's in lecturing mode.

"A refresher for anybody who's listening: the Natalie Ferno fiasco is what happens when someone other than Caz is on security duty. It's what happens when Scott fucking Parajsa decides to hit a person for no good damned reason and then delegates the hit to external third parties who'll screw it up at any cost. Instead of, for example, me.

"Where is he right now? Drunk? In Chile? Best place. It's a travesty that we left him his privileges.

"I am one hundred percent in favour of killing people who need to be killed. Natalie Ferno did not need to be killed. Wiktor Czekanowski, may he rest in peace, did not need to be killed.

"Who knows what Ferno would have done if she'd linked the attack back to us?"

*

It's months later, the following year. Over coffee, Laura has just given Natalie two gifts: a self-defence shield spell, and a warning. "Be safe."

Natalie spends the whole journey home checking over her shoulder and working out what she needs to do to be safe.

Suppose someone really tried to kill her. Not her sister, at random. Her. On purpose. They botched it, and lay low for months. Why didn't they come back? Will they? When? She knows nothing for certain. But the probabilities are high enough that she can't ignore them.

She has never felt like this. It's as if the whole outside world is flooded with ionising radiation. Being in public is dangerous exposure, and the longer she stays there, the more likely she is to die.

First of all, she tries the shield out. She can't make it work. She has just enough capability to understand that the gift, EPTRO , is far beyond that capability. Next, she rearranges her academic schedule to allow time for a self-directed crash course in applied magic and twenty hours of structured meditation per week. Knowing the exercises isn't enough. She needs to get her mind back into shape.

Once she can reliably cast the shield, and has tested its capabilities, Natalie's simmering fear begins to level off. The need to carry both the bangle and the driver dot is still a liability. She gets one ear pierced, and carries out a highly specialised optimisation computation that enables her to discard the bangle entirely.

Suppose someone tried to kill her. Why?

Natalie reviews every page of work she's produced since her education in magic began. She eliminates the obvious-- that is, the results that are known to the whole world. This leaves her with a relatively small pool of what are essentially magical doodles. She cross-references by time frame, reducing the pool further. But it's just paperwork. Theory.

What about practice?

Practical magic releases floods of chi particles. Chi particles are usually described as neutrinos with attached metadata. They are almost non-interacting unless deliberately intercepted.

Natalie imagines the Big Brother future. She imagines the magical equivalent of a directional microphone, trained directly on her head, recording every spell she ever casts. Natalie works with theory. She can enumerate almost every spell she ever cast, there are so few.

She imagines everybody in the world with an identical microphone pointed at them. Has anybody else ever cast a spell she wrote? Could that have been tracked back to her?

Oscillating crazily between conclusions, she calls Zeck's number.

The person she reaches is his widow.

The last winter, Natalie learns, had been too hard for Zeck. He became terribly ill, terribly quickly. Pneumonia.

*

"Caz, another thing. Did you say Nat Ferno witnessed the bombing of her sister's house?"

"Yeah," Casaccia tells Exa. "That's what the news is saying."

"From where?"

Casaccia pulls the relevant feed up again. Delving into the records like this is starting to bring on a headache, because he's not doing it the right way. Scin, the seer, would be able to do a better job, but is still hours away.

Shortly, Casaccia will remember that he is a Wheel Group member, and set his kara to chase the headache away. But he's going to suffer for another twenty or thirty minutes before that.

"She--" he begins.

Exa responds with patient silence.

Casaccia is now looking at a single frame with three labelled green pinpricks. "She was one of the two who were blown up."

"Natalie Ferno gave the police an eyewitness account of the bombing... from beyond the grave?"

"I'm watching in slow motion," Casaccia says. "They weren't killed. The bomber dies instantly. She and the other man... exit the house at high speed when the detonation takes place. Blown away. A few minutes pass and they get up. Perfectly healthy. ...Could they have been wearing medrings?"

"Or some kind of shield," Exa says. "We repossessed Rachel Ferno's medring, there's no way she passed anything similar down to her heirs. Without being stupid, could they have survived if they were wearing bomb-disposal gear?"

"Impossible," Casaccia says.

"A shield, then," Exa concludes. "They survived using magic."

Casaccia frowns, winding the feed back and forth. "Erm."

"'Erm'?"

"Give me one second."

There is no chi on the feed.

Maybe the bomber's akashic scrambler had a wide field effect. Wide enough to blot out everything out to Natalie Ferno's final resting place, on the other side of the street.

But the bomber dies. Less than a tenth of a second after detonation, he has ceased to exist.

And there's still no chi on the feed.

*

It's months later still and Natalie is flying home from Iceland with her mind racing. Frightening, inexplicable things have just happened. Ra isn't the half of it.

("This isn't you, Benj! So who is it?" she had shouted at him. "I told you," he had replied. "I've been telling you and telling you--")

Her mystery spell - well, subspell - is an odd piece of rough working. She can compute, to any number of decimal places, what it really does. What she can't predict is how reality will react to it, which means she has to try it and see. But if she tried the spell in reality, chi would flood out and give her away, just like it gave Zeck away. It would mark her as a confirmed threat. To whom, she doesn't know. She can't know that yet.

She could suppress the chi output. That much, she has (with difficulty, in secret) proven. But suppressing the output would require a whole different spell, and that would release its own chi, which could still be tracked. She'd need to suppress the chi output from that second spell using a third. And so on, recursing forever. In theory, it could be done very easily... using a spell which was infinitely long and infinitely complex, because no finite spell can completely describe its own structure.

Unless, that is, you know the first thing about quines.

Natalie Ferno thought quine spells couldn't exist. And then, on the mountain a few days ago, she saw a counterexample with her own eyes.

Natalie doesn't know that Benjamin "Ra" Clarke built his quine with mechanical assistance from an astra, an ungodly dangerous artifact from before the dawn of time; a machine which enables spells to cast spells. With that object in one's hands, building something like an akashic scrambler is made shockingly simple.

But Natalie also doesn't know that the artifact in question is just a shortcut, a labour-saving device. Like riding a helicopter to the peak of K2, it does nothing that a sufficiently determined human being couldn't do unaided.

Theoretically.

All Natalie knows is that it's possible.

*

"She's wearing a scrambler as well," Casaccia says.

"For how long," Exa asks carefully, "has she been wearing it?"

"I don't know," Casaccia admits, exasperated. "I don't know! I'm working on it. I haven't had five seconds in a row to think about this yet."

Exa says, "Scott Parajsa acted because of a worst-case scenario in which Natalie Ferno, or Wiktor Czekanowski, or both, had used that oracular spell and had seen the listening post, or the distributor, or both. Or worse, Ra. Nat Ferno found a loophole in magic through which she would be able to see us. But all the evidence suggested that she was dropping the thread. That it was a non-issue. We set tripwires just in case it became one.

"And now?"

*

It's months later, months later, months later again--

Natalie Ferno, thaumoastrophysicist, is looking for evidence of magic in space. The project is ongoing. It's too early to judge yet, but she already knows what she's going to find.

You can't prove a negative. It doesn't matter how much data you gather. It will always be possible to rationalise the gathering of additional data for the purposes of confirmation.

It will always be possible to justify withholding the truth. One more month. Two more months.

Laura Ferno is a bad scientist-- rash and far too reckless. And Natalie Ferno is a bad scientist too, in her own way.

*

Exa doesn't let Casaccia get a word in. "Parajsa's bad call made the worst-case scenario happen. We're so far beyond it that we need to recalibrate. Who knows how long she's been hiding from us? Who knows what she's actually seen?"

*

It's now.

In Chedbury Bridge reception, Natalie Ferno has assumed the "thinking king" pose: slouched to one side in an armchair, the fingers of one hand against her temple and cheek, staring directly forwards at something extremely important which nobody else can see. Beside her, her coffee is levelling off at room temperature.

She and Devi have been locked out. They're off the case now, too close to the source material to be allowed to pass judgement. Certainly, they've been kept separate from any and all instances of Ra. With a little effort, the police will be able to find other, independent mages to pick the pieces up.

This leaves Natalie with a very small pool of known facts.

There's a telescope pointed down into the Earth. I walked past it twice. Once on the way in. Once on the way out.

It had moved. I know it moved, because I was looking for it.

There is a way to make sense of all of this. Even without access to the evidence that the police are holding, there is a straight line through to the far side. But she can't find it.

"I'm sorry," Anil Devi says, sitting near her with his own drink.

Natalie carefully avoids reacting to him.

"I'm sorry about your sister," Devi continues. "I barely worked with her, but... she was a great engineer. Forceful. Uncompromising. She almost always had the right answer."

"She and I died once before," Natalie tells him, not moving. She speaks softly and lightly, as if reciting a fairy tale. "We were on a volcanic mountain in Iceland, called Krallafjöll. We were there with a friend named Benjamin Clarke. He had been possessed by Ra. He blew the mountain up below us, and we drowned in lava.

"We survived inside a shield, perhaps for ninety seconds, or two minutes. Then Laura and I ran out of mana, and the shield collapsed on us, and we were killed. Crushed to ashes and burnt to atoms."

Devi has no response to this.

Natalie says, "Before running out of air, we escaped into T-world together. And while inside the dream we watched ourselves die. And then all three of us, Laura and the real Benj and I, walked home from the dream. And I still..." Natalie doesn't finish the sentence.

"How did you walk home?" Devi asks, gently.

Natalie ignores the question. "We did it once. Laura can do it again. She's alive."

"No." Devi takes Natalie's hand. "Your sister's dead. So is her boyfriend. You saw the buckets. You identified what was left." Devi is having to steel himself to say this, because he, too, has seen the buckets, and Jesus Christ.

"This all began with a conservation violation, Anil," Natalie tells him. "Laura's still alive. She's still in trouble. And we still need to find her."