"What happened?" Headmistress McGonagall asked upon entering the Arithmancy classroom. Mr. Bones, seventh year Ravenclaw, had fetched her from her office at a dead run and had given her no other explanation than that there was something wrong with the professor.

"I don't know, Professor," Mr. Bones said. The other students looked just as scared and helpless as he did, perhaps more so. At least Mr. Bones had had the presence of mind to fetch her. "Professor Granger was talking about our seventh year projects and then she just… stopped."

"Look at her eyes," Miss Smithe said from the first row. The girl was Slytherin. This was the seventh year class; all the Houses were mixed together as there were only six students in the class.

McGonagall glanced at Miss Smithe, who was frozen in place with a haunted look on her face, before finally fixing her attention on the witch at the front of the classroom.

Hermione had been teaching for almost ten years. She was competent, good with the children. She stepped in once a year for a History of Magic lesson on the second war and the Battle of Hogwarts. (Binns didn't seem to notice.) She was an asset to the school, and McGonagall was glad to have her around; they were friends.

After the war, Hermione had disappeared for awhile. She'd gone to Australia for her parents and taken an apprenticeship with an Arithmancer there, earning her mastery before returning to London. She'd worked for Gringott's for awhile (doing something with financial futures or some such) before agreeing to teach. She was quiet; the only time she talked about the war was that one day a year for the class. She kept in touch with Potter and the Weasleys, McGonagall knew. She'd come through. She was friendly with the other professors, even Snape. (The more shocking thing was that Snape seemed to tolerate her as well, if only just.)

Looking at her there at the front of the classroom, McGonagall was put in mind of the young woman she'd seen chasing after Potter during the battle. She was frozen in place, face blank except for the eyes. The eyes were open wide with absolute horror.

"Professor Granger?" McGonagall asked softly, stepping around the desk to stand beside her professor. Hermione didn't move. "Hermione?"

When she reached out to touch the younger witch's shoulder, the room seemed to explode with white fog. It billowed from nothing, filling the room with swirling mist. McGonagall twitched to pull her wand, but she couldn't remove her hand from Hermione's shoulder.

The mist filled with images, then sound rushed in as well. McGonagall saw a younger version of herself walking toward the front of the classroom with the Sorting Hat, looking tattered but not quite so bad as it was these days. The image changed, and it was a gigantic troll lifting a club, a vacant look plastered on its face, a barbaric yawp echoing off phantom bathroom fixtures. Then it was McGonagall again, this time striding forward with a dangerous look on her face, the castle's suits of armor and a few statues following her with their weapons at the ready.

McGonagall finally broke contact, stumbling back. The mist vanished as quickly as it had appeared.

"Come to the Arithmancy classroom immediately," she said, sending her Patronus off with a flick of her wand. The students were in their desks, each looking stunned. "You are dismissed; gather your things," McGonagall said, but none of them seemed to be able to move, and she couldn't bring herself to look away from Hermione long enough to make them.

Hermione twitched, making everybody in the room jump. Her eyes shifted to McGonagall, her face taking on a politely inquiring expression, but then it was gone and her eyes were far away again.

The room filled with fog again, this time darker. The fog formed the shape of a dusty room, and there was a very skinny, very scruffy Harry Potter scuttling backwards away from the snake Nagini. Then there was a younger Hermione, as too-thin and drawn-looking as Potter, rushing in, casting curses at the attacking snake. Then the mist Hermione grabbed Potter and they crashed out a window, the sound of it shattering made McGonagall flinch even as the smoky shards dissipated into the larger cloud. There was a crack of Apparation, and the mist Hermione and Potter were in the woods, Hermione crouched over a bleeding Potter, crying and apologizing.

The door banged open, dispelling the fog. McGonagall jumped, bringing her wand up only to drop her hand to her side a moment later.

"Severus."

"Headmistress?"

Snape looked the room over, taking in the rigid shock of the students and the eyes of the professor at the front of the room.

"Has anybody touched her?"

"I did," McGonagall said, feeling immediately relieved when he sounded like he knew what was happening. "There was fog…"

"Yes." Snape strode into the classroom as familiarly as if it was his own. When he reached the front of the room, he turned to look at the students, glaring. "Get out."

A few of them twitched, reaching for bags, but none actually got up. McGonagall didn't blame them. A few were still looking at the spot on the floor where the fog had formed the blood that had begun to pool beneath the Potter apparition.

Ignoring the room, Snape stepped around the desk and grabbed Hermione by both shoulders, turning her bodily to face him. "Hermione," he said sharply and her eyes darted to his. McGonagall had a moment to be surprised at the familiar address before the room erupted in fog again, thicker this time.

Images flashed through the room quick as thought. A Snape without any gray in his hair jumping up and stomping on the flaming hem of his robes. Snape leaping forward to contain an exploding cauldron while a very young Hermione darted into the ingredients storage cabinet. Snape rising tall in front of little Hermione, Potter and Weasley, putting himself between them and an approaching werewolf.

Sound joined the images as the fog grew darker.

"Clear your mind," Snape growled, looming over a teenaged Hermione. The teenager, surprisingly, shoved him bodily away from her.

"It'd be easier to clear my mind if you'd stop yelling at me!"

Snape's lip curled in a snarl, but then the image was gone. It was replaced by his form flying through the air unassisted, passing very close to Harry Potter on a thestral, clutching to it with a look of utter terror on his face. The classroom was filled with screams and the whistle of phantom wind.

Then eerie silence. The fog formed trees, thickening along the floor. The young Hermione looked too-thin again, exhausted, and the Snape facing her a few paces away was just as haggard. They looked at each other, almost glaring.

The next memory was explosively loud compared to the silence. Hermione was on the floor of a richly decorated parlor, a large chandelier hanging above her. She was screaming, writhing. Bellatrix Lestrange stood over her, torturing her. The word "mudblood" had been carved into Hermione's arm, a familiar scar now but bloody and fresh in the fog. Hermione's screamed filled McGonagall's head; she wanted to cover her ears, but she couldn't move.

There was a commotion, but the fog was too thick to see what was happening. Then the chandelier was falling toward Hermione's prone form on the floor below…

It was the Battle of Hogwarts. Hermione was running through the castle with Ron Weasley, dueling as they went, cursing and dodging, stumbling, dragging each other along.

Then quieter again, and it was the Shrieking Shack. McGonagall couldn't look away, but she wanted to be able to. Hermione was kneeling by Snape, a large black kit open next to her as she desperately tended the snake bite. McGonagall had only seen him after, only heard the story. A revised story, if this memory was anything to go by—Hermione was bloody up to her elbows, blood smeared across the front of her shirt and smudged on her face where she'd touched pushing her hair back. She was crying but trying not to, swearing at her patient as she worked.

His neck, even the shadow of it formed by the fog, was a mess. A huge chunk of flesh was missing, and it didn't seem to want to stop bleeding. Hermione applied pastes and globs of flesh-colored something, forcing potions down Snape's throat between each application. Then she was applying a potion that made his flesh steam and he screamed. She bandaged him, smudging more blood across her forehead when she wiped away the sweat.

"Hermione," Snape, the real Snape, repeated at the front of the room.

"I submit this testimony on behalf of Severus Snape," the new fog form of Hermione said. She wore the black formal robes she'd worn so often to court for the trials following the war. The panel of ghostly wizards shifted uncomfortably as she approached; McGonagall remembered that, by the end of the trials, most of the Wizengamot had dreaded Hermione Granger. She'd testified for or against almost every single person who'd had charges against them, and her testimony, almost every time, had aligned decisively with the verdict. It had helped that, whenever there had been even an inkling of doubt, Harry Potter, the Chosen One, had arrived to back her despite his otherwise surprisingly lack of public appearance for years following the Battle of Hogwarts.

The image in the fog shifted once more. Hermione and Snape were in Muggle clothes—Snape in blue jeans was a thoroughly odd sight—walking down a Muggle street, probably in London. They each held a little paper wrapper of fish and chips, and they were eating and talking, comfortable with each other. It was a recent memory; the Snape in the fog had those strands of gray at his temples that were new.

The fog vanished. "Again?" Hermione asked from the front of the room.

"Yes," Snape said.

There was a flash of fog, very brief. Snape's form, curled into a ball in the center of the room, screaming and clutching his neck. A ghostly Hermione rushed to him, grabbing him by the shoulders. Then the fog was gone.

Hermione drew a shuddering breath at the front of the room, slowly sinking to her chair.

"What was that?" McGonagall asked, leaning against a student desk, grounding herself with the feel of the warm wood beneath her palms.

"A flashback," Snape said, matter-of-fact. He stood behind Hermione's chair like a guard, arms crossed over his chest. He was very tall. It made Hermione look even smaller than she was, sitting there.

"It happens sometimes," Hermione said, her voice shaky. McGonagall noted that Snape shifted his stance so that his weight was on the leg closer to Hermione; he was leaning toward her ever so slightly. "With Occlumency and Legilimency… memories can be amplified sometimes. You get… caught up. It's hard to break out of them."

Hermione began to shake. She wasn't crying, and McGonagall didn't think she was going to, but she was practically twitching she was shaking so badly. Snape surprised her by unfolding his arms and putting a hand on Hermione's shoulder. It calmed her immediately.

"Show's over," Snape said, somehow managing to look sharp and annoyed even bent forward to comfort his colleague. "You are dismissed."

The students slowly packed their things and left the room, filing out in utter silence. A few looked behind them as they went, glancing at the front of the classroom, but they met only Snape's hard glare. Hermione had closed her eyes, breathing deeply.

When the room was empty, McGonagall suddenly felt as though she was intruding. She hadn't realized Hermione and Snape were anything more than civil to each other.

"I didn't know you'd taught her Occlumency," McGonagall said, trying not to sound as wrong-footed as she felt.

"Of course I did," Snape said, letting the tone of his voice convey the eye roll instead of actually rolling his eyes. He stepped back and drew Hermione out of the chair and into a hug. His taller form completely enveloped her, his robes closing around the small witch, tucking her into a cocoon. "We were trying to teach Potter, and you and I both know that Potter learns best by osmosis. Teach Hermione, and he gets it from her." In his arms, Hermione laughed, pressing her head to his chest, then stepped away. They stood very close, not quite touching. "It didn't work, of course."

"But it wasn't Legilimency anyway," Hermione pointed out. "It was the Horcrux in him."

"Yes," Snape said, more acknowledging the point than agreeing with it.