Disclaimer: If you're reading this, you probably know the drill by now. All maths in this story is real and correct to the best of my knowledge. All arithmancy in this story besides the tiny amount mentioned in the books is stuff I made up. JK Rowling owns the rest.

Cover art adapted from alex heesher 9, also known as aheesher on DeviantArt.

A/N: Well, here it is, the third and final instalment in the Arithmancer Series. The first two stories in this series went on way too long in retrospect—as long as the original books! But I had a lot of fun writing them—so much so that I wanted to do a continuation after the war. Annals of Arithmancy, however, will be much shorter and more episodic, showing the continued developments in Hermione's life in the years after the war.

Just for some housekeeping stuff, I'm currently planning to put up a new chapter of Animagus at War next weekend. I'm trying to cycle through my stories once before deciding what to focus on, so we'll see where it goes.

Chapter 1

1 June 1998

This office was probably meant to be comfortable and soothing for patients, Hermione Granger thought. There was no desk and no sofa for the doctor to look down from a seat of power—just two soft, comfy chairs facing each other. Hermione sat uncomfortably in one of them, remembering. She had been only twelve the first time she was here, a fair bit smaller and getting lost in the overly soft cushions, trying to come to terms with the experience of seeing a man supernaturally murdered before her eyes. There were days when she wished she could go back to that carefree time when that was the only thing she had to worry about.

The room hadn't changed much in the past six years. Same stereotypical bookcase, potted plant, abstract art, and small windows to let in some light, but not so much that it lost its homey atmosphere. It was smaller than the stereotypical office she saw on the telly, though. Again, it was probably to make it feel more intimate and comforting, but now that she'd returned, it just felt confining to her.

The other woman sat in the chair across from her. She was about her mother's age, but they didn't look a whole lot alike. Her hair was straighter and more of a chestnut brown than her mother's dark brown; her face was more pointed, and (Hermione couldn't help noticing even after all these years) her teeth weren't quite as nice. She still wore a kindly smile. Dr. Sylvia Hudson.

Her therapist.

"Well, look at you, Hermione," she said. "You're all grown up now."

Hermione shifted awkwardly. This seat was still too bloody soft. "Thank you, Dr. Hudson," she said stiffly. She didn't really know what to say to that. In some ways, she felt like she'd never really had a proper adolescence. She did look more adult and put together, now. Dr. Hudson wouldn't have missed her engagement ring, nor her other jewelry—understated, but clearly expensive. She was probably dressed a little more professionally than was called for, but at the moment, most of her wardrobe still said either "too busy not dying to care" or "literally a witch," so she didn't have much to work with, not to mention how she had felt the need to wear long sleeves despite the warm weather. Too many questions otherwise.

"I get the feeling a lot's happened since we last met," Dr. Hudson said.

Hermione chuckled ruefully. "Yes, you might say that."

There was an awkward silence for a minute, and when she didn't say anything more, Dr. Hudson asked, "So who's the lucky man."

She smiled at that, glancing down at her ring: "George. I must have told you about him. One of the twin class clowns? The last you heard of him would have been when he took me to the school dance."

"Oh, so you've stayed together?"

She wiggled her hand back and forth. "It took us a few more months to really admit it to each other, but basically yes."

"That seems like an interesting pairing for you," she offered.

"I know. That's what everyone said. But he's smarter than he lets on—more responsible, too. And he makes me laugh. You know, he and his twin already own their own shop?"

"Really? What kind of shop?"

"A joke shop, of course. They sell…you know, pranks and stuff…" Hermione trailed off. She'd never had to explain Weasley's Wizard Wheezes to a muggle before, and it suddenly occurred to her that she'd never in her life seen a joke shop in the muggle world. Maybe a store for "magic tricks," but never one for just pranks. Strange that she'd never noticed that before. "It's sort of like a cross between a toy store and one of those weird novelty stores. It sounds mad when I say it, but they're very good at it."

"I can imagine," Dr. Hudson said with a smile.

"Only, it got firebombed last year. We're only just now getting around to rebuilding it."

Dr. Hudson's mouth dropped open for a moment. She quickly recovered, but she grew more serious again. "Hermione, I…I think you'd better explain," she said. "If I may say so, you have a look about you that I usually only see in war veterans, and the things I've been hearing about you…"

Hermione tensed perceptibly. "What have you been hearing about me?"

Dr. Hudson leaned back and folded her hands. "You seemed to have the worst luck as a student. A teacher murdered in Year 7 and near-deaths the next three years. When I last saw you three years ago, you seemed more distant than before, but when you didn't show the next summer, I thought maybe you finally had a normal year…and then six months later, I heard about your house being firebombed. I thought you might be dead for a while, but then, four months ago, they said you joined the IRA and blew up a hospital! I actually called the police and told them there was no way you would join the people who killed your parents."

Hermione gasped softly. Depending on how far that call had gone… "What did they do?" she asked.

"Some really scary-looking people showed up at my home and told me you'd killed your own parents, and I'd better not tell anyone anything different."

"Merlin," she breathed. "You're lucky that's all they did. Okay, it's a long story. First off, my parents are still alive. I did burn down our house, but it was a cover. I had secretly moved them out to Australia the previous day."

"They're alive? Well, I'm happy for you. And I did hear the report that you'd been exonerated. So…I'm guessing you were on the run from the IRA that whole time?"

Hermione shook her head: "No, Dr. Hudson. I was on the run, but it wasn't from the IRA. Or the government, mind. The real story is a bit less believable."

"Frankly, Miss Granger, at this point, I think I'd believe anything."

She smirked and pulled out her wand, "Well, we're about to test that," she said. "Legally, I'm not even supposed to tell you this, but confidentiality is still in play, right?"

"Um…yes, but frankly, I'd really rather not be privy to classified government secrets."

"Don't worry; these secrets are not classified by any government that has authority over you," she said. She held up her wand for Dr. Hudson to see. "This…is a magic wand."

"A…magic wand?" she asked.

Hermione nodded. She waved it, and the curtains were drawn closed. Dr. Hudson jumped in her seat. She waved it again, and the little table between then began to run around the room like a puppy. Dr. Hudson yelped and looked like she was about to faint.

"I'm a witch," she said. "And I was on the run from an evil wizard these past few years."

Hermione explained. It was hard to fit seven years of her life into half of an hour-long session, but she did the best she could. Magic was real. There was a hidden community of witches and wizards all over the world, scrupulously kept secret from the non-magical, "muggle" world, and she was a part of it.

"And if I tell anyone, those really scary people will come back?" Dr. Hudson asked.

"No, those people are gone now," she said. "It'll be less scary people this time, and they'll wipe your memory of me, not threaten you."

"What? But…how is that better?"

"It's not, really. I'm on your side there, but most wizards don't think the same way we do. And frankly, the other option is to tell everyone you've gone mad, so…"

"Right," she groaned.

Hermione went on. The exclusive boarding school in Scotland she'd attended was a premier school for magic. She was a rare person with magical born to muggles, and she had been found by the school and had entered that world at eleven. She explained her previous visits first. The teacher who was murdered in her first year was possessed by the spirit of an evil wizard who hated muggle-born outsiders like her. The snake that had "bitten" her in her second year (though it really hadn't) was a fifty foot-long basilisk that had nearly killed her with its gaze. The escaped convict in her third year—well, that was pretty close to how she'd described, except she hadn't mentioned the soul-sucking demons before. Oh, yes, and wizards had tangible evidence of the existence of souls, too.

At the end of her fourth year, she said, Lord Voldemort had returned from the dead, and things just spiralled out of control from there until the magical world was at open war.

"So all those IRA attacks…?" Dr. Hudson asked.

"The ones in the past one to two years were mostly Death Eater attacks," Hermione confirmed. "Including the one at the Nottingham hospital. My fiance's brother and great aunt were killed there."

"It sounds like you lost quite a few people," she said sympathetically.

Hermione nodded. "Six I'd consider good friends, others whom I considered close mentors, and dozens of other acquaintances, including other classmates."

"Goodness! I'm sorry for your losses, Hermione. I'm glad you've sought out help again. These kinds of traumas can be devastating for anyone."

"That's one of the reasons, yes," she confirmed.

"Oh? And the others?"

"I…This is going to sound daft, but I feel like I don't know what to do with myself now that it's over."

"Ah. That's an understandable reaction," Dr. Hudson said. "There's no need to worry about that. Fighting this war was such a large part of your life, and now that it's gone, you need time to adjust."

"Maybe," she admitted. "I did have plans—still do have plans, in large part—but now that I'm finally here…well, it's less appealing than it was before, at least."

"That's not uncommon either, Hermione. The grass is always greener, and all that. But that doesn't mean your plans were or are bad ones. What were you planning to do?"

Hermione shrugged. "I thought after the war, I'd go back and finish school, get my mastery in Arithmancy, get married, and start a relatively quiet career doing magical research. And I suppose I can still do most of those things, but I definitely can't get my mastery now."

"Why not," she said, confused. "It sounds like you're more than capable."

Hermione gave Dr. Hudson a level stare: "Because they already gave me my doctorate."

One Week Earlier

"Hermione Granger," said Professor Tinworth, "in consultation with Headmistress McGonagall, Griselda Marchbanks of the Wizarding Examinations Authority, and Head Unspeakable Algernon Croaker, I am pleased to inform you that you have been awarded the Doctor of Wizardry degree in Arithmancy."

Hermione stared at Tinworth for a minute, her expression flat. She had only come in to discuss resuming her mastery. "Excuse me?" she said.

Tinworth flinched. He seemed a little nervous around her. It was true, she hadn't got on with him when he the lead editor of Annals of Arithmancy and had turned his back on her under political pressure from Dolores Umbridge. So she supposed he had some reason to be uncomfortable around her, but this had nothing to do with that.

"I took the liberty of contacting a panel of accredited experts, and we agree that you qualify for a DWiz degree," he said.

Nope, she still couldn't process it. "Is this some kind of joke?"

Tinworth flinched again: "No! I simply thought that given the unfortunate matter of the Wenlock Prize—"

She groaned. She'd been meant to received the Wenlock Prize for helping to prove that radioactive material was a sixth exception to Gamp's Law of Elemental Transfiguration, but that wasn't the point. "I don't care about the Wenlock Prize, Professor Tinworth," she said. "I don't need some medal to validate me. What I want to know is how you can give me a doctorate when I haven't even finished my mastery yet, let alone a dissertation."

"Miss Granger," he said, looking a little relieved, "we don't do things the same way as in the muggle world. A mastery requires a major research project—a 'masterpiece' in the old parlance, but the DWiz is awarded for extraordinary scholarship in general, not a specific dissertation. The two main criteria are an extended body of scholarship and research as a Master, and a major contribution to the field above and beyond the mastery level, but that's not the same as a masterpiece. Many people earn a DWiz by writing a textbook. And when it is a research project, it's often unpublished for a good reason."

"But I never qualified for a mastery in the first place," Hermione protested.

He shook his head insistently. "Your work on Gamp's Law is more than enough for that, even working with a team. And Professor Vector told us about your continuing education, which fulfils the apprenticeship requirement for the mastery. For the DWiz, she told us enough about your ongoing research to prove your continued scholarship, and if Killing a dementor doesn't represent a 'major contribution,' we may as well bin the whole field."

Hermione sat back in her seat. "Doctor of Wizardry," she muttered to herself. "What does that even mean? I've never seen a wizard addressed as 'Doctor.'"

"Well, they used to be," Tinworth said. "Before the muggles bastardised the term—no offence. It's 'Professor,' now. That is, in addition to recognising you as one of the premier scholars of the field, the Doctor of Wizardry entitles you to use the title 'Professor.'"

And that was when Hermione cracked. She started laughing and couldn't stop at the sheer inanity of the situation.

"I'm going to go back to school in September as 'Professor Granger'—the same title all the teachers have," she told Dr. Hudson. "How ridiculous can you get? I mean sure, George thinks it's the best prank ever, but really! I'm not the youngest woman ever awarded a doctorate in Britain—not even in maths. I checked. But I'm certainly the youngest witch, and I just can't get over how absurd it is. Plus, in the magical world, I can't even tell people to address me as 'The Doctor' without everyone looking at me funny."

Dr. Hudson chuckled. "Trust me: the novelty wears off quickly," she said. "Still, I should think that it's a good thing on the whole."

"It is a good thing," Hermione said. "It's just that…well, look at me. I'm eighteen years old. I've already reached the pinnacle of the career I've wanted since I was eleven. I haven't even finished school, and I wouldn't need to if I didn't want to at this point. I've won a war. I've slain demons. I'm world-famous in the community where I live, and I make enough money from my hobbies that I'll never have to work a day in my life…After all that, I don't see what I could ever do going forward that would be as significant as what I've already done…And then I'm a mathematician, and a lot of mathematicians do their best work when they're young anyway…"

"Ah, I see," she said kindly. "Would you say, then, that you're struggling to find meaning in your life?"

Hermione thought about that. "Maybe," she conceded.

She nodded to her. "That's something a lot of people your age feel when they leave home for the first time and are free to do what they want. Now, I think it sounds like you actually have quite a lot from which you can draw meaning, but I can see how it would be hard to compare that with what you did in the war."

"Yes, yes, I suppose that makes sense," Hermione said.

"And the war seems to have been a great struggle for you personally," she continued. "Another common problem that you seen where there's a war is returning veterans struggling to find their place in the world while also dealing with the trauma they've experienced. That can make it that much harder."

Hermione sighed. "Yes, I think that's definitely part of what I'm feeling," she said. "The war's changed me, I know. My parents have noticed. I've noticed…I'm a little more afraid of my temper than I was before, to be honest." She thought about the desperate moment at the very end when she took down Bellatrix Lestrange…but she pushed the thought away.

"And that's something else we can work on," Dr. Hudson said. "I think I've got a fairly good handle on what kind of help you're looking for now, Hermione. I don't want to raise your expectations too much; it's going to be a hard process, but it sounds like we have at least all summer to work on it." She thought for a minute and added, "And let's start with that second concern first, because that's the one that can often cause the most severe harm. Have you had an assessment done for post-traumatic stress disorder in the past month?"

Hermione shook her head and settled uneasily into the cushions.

4 June 1998

"Cornelius Oswald Fudge," the Chief Witch of the Wizengamot intoned, "you have been accused of the following crimes: breach of oath of office, abuse of authority, criminal negligence, reckless endangerment, taking bribes, conspiracy, unlawful use of Ministry resources, unlawful interference in an independent institution, namely Hogwarts School of Witchcraft and Wizardry, and aiding and abetting a criminal, namely Dolores Jane Umbridge. How do you plead, Mr. Fudge?"

"Not guilty!" Fudge exclaimed to the Wizengamot chamber.

"Very well," said Andromeda. "The prosecution may call its first witness."

A wizard Hermione didn't know rose to his feet and said, "I call Sirius Black as witness." Hermione watched as Sirius took his place in the witness's chair to testify to Fudge's handling of the investigation that saw him sent to Azkaban.

By the time the war ended, the Order's top five or so choices for the leadership positions in the Ministry were all dead, so they'd had to make do and cobble together anyone they could to run a transitional Ministry until elections could be organised. Thus, at the moment, Andromeda Tonks was acting as Chief Witch; Percy Weasley was the Transitional Minister for Magic, and Hestia Jones had reluctantly taken over as the Head of Magical Law Enforcement. Hermione was just glad she didn't have to serve as prosecutor on top of everything.

The first round of Death Eater trials had gone remarkably quickly. For those who had escaped Azkaban at any point, be it in the first war or the second, the trial was merely a formality before they were sent back to prison. The hardest part was figuring out where to actually put them. Percy had decided the Ministry should turn over a new leaf and stop using dementors as prison guards, just as Dumbledore had wanted for a long time. Hermione wholeheartedly agreed, but that meant Azkaban was out of the question, since no one could figure out how to get the dementors to leave, or where else to put them. She'd heard a creative proposal to build a new prison on the Isle of Drear—he functional equivalent of a castle with a moat filled with crocodiles, except that here they would be Quintapeds. She didn't think that sounded much better. For now, they were simply being held in a heavily-guarded castle in an undisclosed location.

For those who had not been convicted of a crime, however, it was much harder, and a lot of that work fell to her. Percy had made her Chair of the Demortification Committee—magical Britain's answer to Denazification in Germany after the Second World War. (Her own name for it. She didn't really like it, but no one had been able to come up with anything better.)

Building a case against a Death Eater and proving they were acting of their own free will was difficult, even with magic. Rita Skeeter would be an invaluable witness with the information she had collected for Hermione as a spy, but even so, Hermione was shocked when Percy informed her that the case against Fudge was ready to go forward before a lot of the Death Eaters' cases did. But there was certainly a lot of interest. The spectator gallery was packed.

"So how do you think the trial is going to go?" she asked Percy as they watched.

"Hmm, it's a tough call," he said. "We threw everything we could at him, but a lot of it is subjective. There's a lot of wiggle room to say he was only incompetent as Minister, not criminal. But on the other hand, everyone knows he was responsible for V…Voldemort rising to power again. I'm worried it'll turn into a…"

"A witch-hunt?" Hermione offered.

Percy glanced at her. "Not the word I'd use, but yes. A fair trial will probably give him five to ten years. I wish I could say it were more, but there's legitimate reasonable doubt."

Hermione sighed. "I suppose so," she said. "I'll still feel better seeing him get his deserts."

"Yeah, me too," he said.

Fudge was only the start, of course, and not the main problem. If they wanted to make this past war count for something, they had to rip out the bigoted ideology that allowed it war to happen root and branch and make sure it never grew again. That was going to be a long, hard fight, and Hermione didn't know what the right answers were any better than anyone else.

What even was justice when a large fraction of the nation's youth had (by muggle standards) been impressed into committing war crimes? Most of the upper year students at Hogwarts had been threatened into casting the Unforgivable Curses on each other last year, something normally warranting life in prison. She'd looked up muggle law, and it didn't look kindly even on the defence of duress for war crimes, but that was for soldiers. As far as she could tell, the question had never been tested for civilians, much less underage ones.

And to be honest, her hands weren't completely squeaky clean, either.

One thing she had going for her, though, was the extensive muggle writing on Denazification in Europe. The Allies had faced the same problem then: too many Germans had been legally complicit in the crimes of the Nazis for it to be logistically possible to fully enforce the law. It wasn't an exact match since there was no foreign occupying force here, but it was probably the closest they could come to truly dismantling the old pureblood hegemony that had ravaged the country for three generations.

But Hermione knew she also had to learn from the mistakes of Denazification as well as its successes. And there were many mistakes. Before the Marshall Plan, many of the Allies were de facto trying to turn Germany into a nation of subsistence farmers to prevent it from militarising again, and even after the Marshall Plan, the program was shut down in 1951 because it was considered ineffective and counterproductive.

Yet some of the ideas, like the schedule of punishments were good ones. People who were merely followers and didn't commit any crimes had fines levied against them and some restrictions on travel, employment, and political rights. Even that might be pushing it for people who had truly committed no crime, but they could do like the British Army had done and only investigate people when they applied for a government job or some other position of responsibility (contrasted with the Americans, who questioned everyone over the age of eighteen). That might be the most important thing for magical Britain to ensure that the ideology didn't grow up again with the next generation.

As for the rest of the Nazis, "Lesser Offenders" were merely given two to three years of probation. Only the serious criminals were imprisoned, many of them put to labour on reconstruction efforts, though Hermione was going to recommend against that last one. She wouldn't trust even a second-stringer like Scabior with a wand.

She also wasn't going to recommend censorship, as the Allies had done. But much stronger enforcement against criminal acts of bigotry, ensuring there was a strong voice in the media to counter any that the blood purists might set up later, and carefully vetting employees of the reconstituted Ministry—those were the the things that might change the culture.

"By the way, I had something else to tell you," Percy said, He lowered his voice and produced a sheaf of parchment. "We finally worked through the parchmentwork on the dementors, like you wanted."

Hermione snapped her head around to look at him. "What did you find out?" she whispered.

"It was hard to trace them; the Death Eaters didn't much care about what the dementors were doing, but we eventually found all the transfer orders. There weren't any for the Ministry's group. The two dozen dementors we found in Ministry holding after the battle were the same ones that were here on the fifteenth of September."

"Penelope," she said.

"It'll be one of that group," he confirmed. "If you can help her…"

"With only two dozen of them? Of course I can. This is excellent, really. I was worried I was going to have to make a deal with the dementors in Azkaban: 'Give me the dementor that Kissed Penelope Clearwater, and I'll spare the rest of you,' or something. I really didn't want to do that."

"Yeah. Good," he said. "I'll start making the arrangements to move them somewhere you can do the ritual."

13 June 1998

"S'ekballo eis to skotos to exoteron, esy pneuma akatharon!"

The dementor exploded as Hermione completed the ritual, the beam of concentrated sunlight piercing through to the ground at her feet. Where it had stood, a swarm of motes of light swirled in the air—all the souls it had consumed over the centuries. The lights floated up into the sky like sparks from a flame where they disappeared out of sight, presumably passing on to wherever they were meant to go. But this time, one of the motes remained. It floated a moment longer, then took off in a streak across the ground toward the south.

And miles away, she would learn later, in a hospital in London, Penelope Clearwater woke up screaming.

"That's it," she said when she saw the soul make its flight. "We saved her." She motioned to George, and he lowered the mirror of the solar furnace to the ground.

Percy smiled. "Thank you, Hermione," he said. "Even though we weren't together anymore, it means a lot to me."

Hermione took the Diadem of Ravenclaw off her head and stepped out of the circle of dead, brown grass where the ritual had been performed. She didn't really need it at this point, but she kept wearing it to ensure she didn't make a mistake. After more than a dozen of these rituals over several days, the remote stretch of moorland was starting to look like the surface of the Moon. Nothing would ever grow in the circle again unless they (at minimum) stripped it to bedrock and replaced the soil, but in her opinion, it was a small price to say.

"What do you think she'll say when she finds out her ex is the new Minister for Magic?" she asked him.

"She'll probably punch me in the face," he said. "She broke up with me because I backed Fudge over Dumbledore when Voldemort came back. She might even campaign against me."

"Oh. But does she know about you smuggling the Ministry's plans out under their noses?"

"I doubt it. We haven't spoken since we broke up. It's alright, though. I deserved it."

"Hm. Well, let's call it a day, shall we?" she asked as George, Harry, and Ginny fell in behind them. "We did what we came to do. We can deal with the rest of them tomorrow."

Percy shrugged and motioned the Aurors to corral the rest of the dementors. This was tiring work, after all. In fact, it had taken over a week to get this far. The ritual could only kill one dementor at a time; it had to be done in fair weather in the morning sunlight, on a different spot each time, and in a place where it wouldn't raise too much suspicion for a patch of ground to have all the life sucked out of it. They could only kill a few of them per day, and it was only because they'd started looking for suitable locations weeks ago that she was able to start as soon as she did.

"You know, I'm getting better at this," she said cheerfully. "Once I learn how to do multiple Patronuses, I might be able to do it on my own with the diadem."

"You don't have to kill all of them yourself, Hermione," Harry spoke up.

"That's a good point," Percy agreed. "You can't kill all the dementors in Azkaban single-handed. It would take years. Have you considered training some other teams to do it?"

She sighed: "I've considered it, but there are problems. For one, the mental state of defiance of the false death is something that has to be trained, like with the Patronus Charm, and it's arguably harder given the mental bias wizards have that dementors are unkillable and soul-destroying. Not many people will be able to strike the killing blow, and I'm not sure what would be a safe way to train them. And even more important, the ritual itself could be extraordinarily dangerous in the wrong hands, so I don't want to give it to anyone I don't trust implicitly."

"But what's so dangerous about it?" Percy asked. "It's powerful, yes, but it does good work."

Ginny answered him quietly, "It's because it comes from the horcrux ritual, isn't it?"

"Exactly," Hermione said. "Or rather, it's based on the ritual I used on Harry, which is based on the horcrux ritual. I took the darkest ritual known, and twisted it to something light—and more advanced. Imagine what could happen if a dark wizard got their hands on it and twisted it to something dark again."

Percy paled. So did Ginny, Harry, and George. She didn't even need to tell them her thoughts on what that darkness might be. Maybe even a ritual to forcibly split the soul of an unwilling victim. It could unleash an evil even greater than the horcrux itself. She wasn't certain that was possible, but she did not want to find out.

"Okay, then," Percy said in a high, nervous voice. "We'll worry about that later, then."

"I think that's the best idea," she agreed. "At least we finally have time, now."