It's surreal when the fourth year Gryffindors and Slytherins walk into her classroom. All these kids who are grown up or dead in her world. When Harry and Ron and her younger self come in, Hermione concentrates on keeping her features neutral.

After introducing herself and calling each of their names, ostensibly so she'll know who's who, she demonstrates the Protego charm and tells them to pair up. She has one of them cast the shield and the other send mild stinging hexes. She did this with her own fourth years earlier in the year, but Barty Crouch was having too much fun Imperiusing spiders to keep up with the syllabus.

They're all paired up with members of their own House, she sees as she walks around observing. She tells the pairs to switch who is protecting and who is attacking, then stops them to demonstrate the charm again herself, pointing out things some of them were doing wrong.

"We're going to change up the pairings and do it again," she says. "Greengrass and Finnegan, Weasley and Nott, Bullstrode and Brown." Sulkily, because they see she's pairing them with rival House members, they pair up as she calls their names. "Patil and Crabbe, Zabini and Potter, Thomas and Goyle, Malfoy and Granger. Is that it?" She looks around. She hadn't meant to pair Neville with that bint, but there's nothing for it now. "Longbottom and Parkinson."

She has them take turns attacking and defending for a couple of rounds, then tells them, "All right, now you're going to attack and defend at the same time. Cast your shield and keep it up while you try to hex your opponent." This is much harder, and there are frustrated yelps of mild pain from around the classroom.

"Stop. Nott and Weasley, up here please," she says. "Not all of you are evenly matched with your opponents, but from what I can see, these two are. Gentlemen, protect and attack, please." They do, and the class watches. She stops them a few times to correct something one or the other is doing, then has them continue until they're both slightly out of breath.

"Nice work," she says. "Malfoy and Granger, your turn."

She watches her younger self duel a teenage Malfoy who hates her. There's more heat behind his hexes than there was in either Nott's or Ron's, but her younger self is giving as good as she gets. "Good," she says, stopping them before anyone gets hurt.

She calls up each pair in turn, calling a few of them by the wrong name or hesitating before getting it right so they won't wonder how she knows all of their names right off.

After they've all had a turn, she says, "In an actual battle, you might be outnumbered. Potter and Zabini, both of you attack me while I defend." They do, and she parries them easily. "Crabbe, join in." Now she has to work. "Patil, you too." She's breathing harder now, and her brow is damp. "Good," she says, stopping them. "Any volunteers want to try that?"

"Against four?" Harry asks.

"Against two to start with."

A few hands rise, all Gryffindor, including young Hermione's. Naturally.

"Thomas," she says. "Longbottom and Parkinson to attack." It's over in a heartbeat, poor Dean cowering as an onslaught of stingers hits him.

"Harder that way, isn't it?" she asks.

"Gods, yes," Dean gasps.

She has the other volunteers try, and as expected, Harry and her younger self hold off the attack longer than anyone else.

"No one else?" she asks, glancing at Malfoy, who nods and comes to the front of the class, where he does a fairly impressive job holding off Finnegan and Greengrass before Hermione calls a halt.

"In battle conditions, you're going to be fighting off any number of attackers," she tells them. "It won't be like a classroom duel. No rules. No limits. It will be ugly and painful and dangerous, and you need to be prepared."

Lavender raises her hand. When Hermione nods, she says, "Professor, you talk like we're going to be in a battle. There hasn't been a war for ages."

"As the Romans used to say, Miss Brown, if you wish for peace, prepare for war."

With all her students tired and somewhat battered, Hermione spends the rest of the class quizzing them on theory to determine what that wanker Crouch did and didn't teach them. She sighs inwardly at the way her younger self's hand shoots up every single time.

"I'd like each of you to come see me in office hours this week so I can get to know you," she says at the end of class. "I'm sending a parchment around so you can sign up for a time slot. It is not optional," she adds when she sees the sneer Malfoy directs at Zabini. "Ten House points will be taken if you don't show up, five if you're late."

When she looks at the parchment as they're filing out, she sees her own more rounded, youthful signature at the top of the page.

"How was your first day?" Severus asks when she comes to his lab after dinner.

"Fred and George were a lot funnier when I wasn't teaching them."

He smirks. "The Weasley twins require creative pedagogy."

"What was your creative solution?"

"I had them watch memories of the worst potions accidents I'd ever seen in a Pensieve during detention."

"And?"

"After I vanished the vomit, we came to a modus vivendi. They would save their mischief for Minerva and Filius, and I'd help them with the nefarious brews they were concocting outside class."

"A beneficial arrangement all around."

"Those boys should have been sorted into my House."

"You like them!"

"Nonsense," he mutters gruffly. "I'd be better able to keep an eye on them."

Hermione hides her smile and pulls a parchment from her bag. "So the Time Turner potion. I brewed enough for several weeks, but had a slight mishap en route and I need to brew more."

"I developed this?" he asks, looking at the instructions. "Bloody brilliant, if I do say so myself."

"It is. But you were still working on it when the Time Turners were supposedly destroyed. Your portrait said he thought it could be improved to extend the length of time I can stay here."

"You don't need more than a few months, I thought?"

In truth, she's nervous about what she'll find when she goes back, and she's in no hurry. She wants to spend more time with Malfoy, because of the promise she made, and with Snape (he's not Severus yet, she reminds herself). She doesn't want to go back to a future where they barely know each other. "I don't think I will, but you never know. And doesn't the thrill of discovery make you want to improve it anyway?"

He gathers the necessary ingredients, setting some of them in front of Hermione and keeping the rest for himself. She sees he's given her the easiest ones to prepare. She sets to work, feeling his eyes on her as she slices and crushes and minces. When he pushes two more ingredients, more volatile ones, in front of her, she feels a flush of satisfaction.

She likes this, working side by side in his lab. After all the time she spent with his portrait, she feels as though she knows him, but it's one sided. He doesn't know her, at least not as anything more than an irritating student. In her time, they teased, they laughed, they bantered with Malfoy and Black and with each other. They conversed so easily, and about almost anything. Even about Dark Magic and sex and what happened the time they dueled.

She knows Severus felt what she did during her demonstration duel, but he hasn't mentioned it. Neither has she. But it hangs there between them, unacknowledged.

When it happened in her sixth year, they didn't acknowledge it either, beyond his vague apology. She was his student and it was best forgotten, or at least ignored, by both of them. So they ignored it. Then he killed Albus and became Headmaster, and she hunted Horcruxes and was tortured. Then he died.

This time, she wants to explore it. He's not her teacher and he's not a portrait. He's a man who, if they're going to brew the Horcrux potion, is going to take her to bed. Assuming she ever works up the nerve to tell him, that is.

"So, five Horcruxes," he says.

"Yes."

"What are they?"

"Rowena Ravenclaw's diadem, which we've already destroyed, a locket that belonged to Salazar Slytherin, a cup owned by Helga Hufflepuff, a ring that was a Gaunt family heirloom…"

"Gaunt. I'm not sure I know that family."

"Riddle's mother and her brother were the last of them."

"Diadem, locket, cup, and ring. That's four. What's the fifth?"

"An accidental Horcrux that Riddle created when he tried to kill Harry and was destroyed himself." She pauses. "A living Horcrux."

"You mean…?"

"Yes. Harry is the Horcrux. The soul fragment is lodged in his scar."

Severus draws in a breath. "In your time…"

"Harry had to die to kill Riddle."

"Did Albus know?"

"He suspected, and by the end he knew for certain. You didn't learn until just before you died that you'd spent the last seven years protecting a boy Albus had essentially raised for slaughter."

"If I have to kill him again, I'll enjoy it this time."

"The truly awful part is that Harry didn't have to die at all. There's a potion to remove a Horcrux from a living host. You had learned of it by then, but not in time to save Harry."

"Do you know how to brew it?"

"Your portrait coached me through brewing the base. We'll have no trouble with it."

"Why just the base?"

"Because that's the tricky part. The rest is easy, and no sense wasting rare ingredients when we couldn't test the finished potion anyway. Not like there are human Horcruxes just sitting around all over the place."

"Show me the instructions."

"They're in a book back in my quarters," she lies. She's not ready to tell him yet what brewing that potion will require. His portrait seemed to think he wouldn't be averse to the idea, but she's not sure. He's not comfortable with her yet, and she'd rather put the conversation off.

"Not in that bag where you carry practically everything you own?"

"Not at the moment."

He stares at her. She's acting strangely, and he wants to know why. He lets it go for now since they're getting to a dicey part of the brewing process, but he files it away to think about later.

When the potion needs to rest before they add the final ingredient, Hermione says, "We'll need to brew Polyjuice next."

"Who – or what – will one of us be impersonating, and why?"

"Lucius and Cissy are going to Gringotts to fetch a Horcrux from dear mad Bella's vault."

He looks at her the way he looks at students who give wrong answers in Potions class.

"It was your idea. Your portrait's anyway."

"It was?"

"It was. He said you wouldn't have a problem getting some of their hair. Though do mind which is which, please. Being Narcissa will be bad enough, but I don't at all fancy the idea of being Lucius." What if they had to stay Polyjuiced long enough to have to use the loo? Having Lucius Malfoy's dick in her hand is not on Hermione's bucket list.

"I'm not the one with a history of mixing up hairs for Polyjuice," Severus drawls. "At least Lucius would be the right species."

"Ha bloody ha."

"Will we need Polyjuice to get the ring and the locket as well?"

"No, those should be easy. I know exactly where Kreacher has the locket hidden at Grimmauld."

"Kreacher?"

"Sirius Black's horrid house elf. I can slip past them using the invisibility cloak and be in and out in no time."

"You mean we can."

"We wouldn't both fit under the cloak. You're too tall. I can do it on my own."

"Or I could do it on my own."

He's not much of a control freak, is he? she thinks. "And if something should go wrong and Sirius should stumble on whoever's getting the locket, I'm the better choice to talk my way out of it. He likes me."

"I'll just bet he does," Severus mutters.

"What's that?"

"I could always kill him if he caught me."

"Reason number 1,347 why I should go. You can get the ring while I'm getting the locket. It's in the abandoned Gaunt house where Riddle's mother grew up. Albus just walked in and took it, from what Harry told me. But you can't put it on. It's cursed."

"What kind of dunderhead do I look like, that I'd put on a Horcrux ring?"

"Albus was exactly that dunderhead. He was dying of the curse when he made you swear to kill him if Draco couldn't."

"The man is a menace."

"The Board of Governors shouldn't let him within a mile of children," Hermione says, stifling a yawn.

"Perhaps I'll have a word with Lucius," Severus says, extinguishing the flame under the cauldron. "Get some sleep. I'll bottle it when it's cooled and you can get it tomorrow. And don't forget that book with the Horcrux potion."