You'll recognize the following flashback if you've read OotP. I tweaked it, but it's still JKR's.

*Edited for brevity, or something.

"LEAVE HIM ALONE!" Lily shouted, her wand pointing at Potter.

"Ah, Evans, don't make me hex you," said Potter.

"Take the curse off him, then!"

Potter sighed deeply, then turned to Severus and muttered the counter-curse. "There you go," Potter said, as if he was speaking to a child who he'd just pat several times on the head, as Severus struggled to his feet. "You're lucky Evans was here, Snivellus-"

And then he'd said it. "I don't need help from filthy little Mudbloods like her!"

Lily blinked.

That was it.

"Fine," she said coolly. "I won't bother in the future. And I'd wash your pants if I were you,Snivellus."

"Apologize to Evans!" Potter roared, his wand once again pointing threateningly at Severus.

"I don't wantyouto make him apologize," Lily shouted at Potter. "You're as bad as he is."

"What?" yelped Potter. "I'd NEVER call you a - you-know-what!"

"Messing up your hair because you think it looks cool to look like you've just got off your broomstick, showing off with that stupid Snitch, walking down corridors and hexing anyone who annoys you just because you can - I'm surprised your broomstick can get off the ground with that fat head on it. You make me SICK."

She turned and hurried away.

"Evans!" Potter shouted after her. "Hey, EVANS!"

But she didn't look back. She hadn't looked back at either of them.

An older Severus was, once again, sitting with his aching head in his hands in his office.

He had replayed this particular memory in his head only a few times over the years; he hated to revisit it. It wasn't the bullying – he had no end of memories in which James Potter and company tormented him. Some of them he liked because once in a while he had managed to pull one over on them, but he was usually outnumbered and those experiences were never pleasant to look back on. This memory was a lot worse, and that was why he hadn't thought about it since the day he joined the Death Eaters. He had been humiliated and impotent in his rage, and he had lost Lily's friendship permanently.

He could never forgive himself or James Potter for that. Forcing himself to remember it now, as fully as he could, made this inescapably clear.

He knocked on their door. Potter answered.

"Hi. We weren't expecting you today. Actually I was at first a little bit nervous that you might have hated the Christmas turkey so much that you'd sold us out, but I can tell by your staunch silence and the faint Snivelly aroma that it's you, which is actually quite comforting, believe it or not."

Severus's brow creased at the use of the old "affectionate" nickname. It was almost as if Potter somehow knew that Severus had taken a trip down memory lane.

"Why don't you come in?" Potter asked, moving backwards into the house.

"Actually, I was thinking we could talk out here, since I don't have anything for you today."

Potter's eyebrows lifted. "Isn't that a bit dangerous?"

By way of answer, Severus undid the disillusionment charm, slowly becoming visible standing on the Potters' front porch. "There's no one here. I checked," he said quietly.

Potter frowned. "What are you playing at?"

"C'mon, Potter, are you afraid to take two steps outside your cozy little house?" Severus almost smirked as Potter started in shock and irritation at the accusation of cowardice. He knew how his old enemy worked.

Potter glared at him, but quietly stepped outside and shut the door behind him. "What do you want, Snape?"

"What I want, Potter, is to make something perfectly clear." He paused, smirking lazily, watching Potter grow more irritated by the second.

"All right," Potter began, apparently doing his best to contain his anger, even though he was nearly baring his teeth at this point. "What is it? What's so important that you're dragging me outside to tell me?"

Severus looked at him. Nothing had changed, really, since the day he'd first met Potter on the Hogwarts Express. He still had that air of having been pampered and well-cared for. His hair was still as messy as it had always been, his face still shone with the kind of arrogance you might attribute to a fussily-kept garden if the flowers could stare down at a weed that had dared grow in their presence contemptuously.

"I hate you, Potter."

Potter blinked.

"I've always hated you."

Potter rearranged his shocked features into an expression that looked slightly less like one a twenty year old wizard in glasses who had just strolled into the middle of an acromantula colony might wear. "I know that!" he sputtered.

Severus stared at him for a moment, and then he seemed to explode. "Of course you know! You know what it's like for me to be waiting on you like this! You know how much I despise being in your house!" Somewhere in the rational part of his mind, Severus was regretting his sudden descent into hysterics, but the wild, almost deranged look on his face as he lunged towards his childhood enemy masked any potential for rational thought behind it to the outside world. James Potter at least seemed convinced of Severus's newfound insanity; he whipped his wand out and held it inches from his old enemy's chest.

"What's WRONG with you?" Potter yelled, and now he really was baring his teeth.

"WHY DON'T YOU HEX ME?" Severus roared. "YOU NEVER SHOWED ANY RESTRAINT WHEN WE WERE AT HOGWARTS! GO AHEAD! DO IT! WHAT'S STOPPING YOU? I DON'T EVEN HAVE MY WAND OUT! OR ARE YOU STILL TOO COWARDLY TO ATTACK ME WHEN YOU'RE NOT WITH YOUR STINKING FRIENDS?"

"I'm warning you," Potter said through gritted teeth. "I'm warning you, Snape. If you don't calm down -"

The door crashed open and both Severus and Potter whipped around. Lily stood in the doorway staring at them. "What's going on?" she yelped.

Severus and Potter looked at each other. Then, simultaneously, Potter lowered his wand and Severus backed away from him.

"What are you two -" Lily began, but Severus interrupted her.

"From now on, you'll leave your lists on the front door, and I'll leave your supplies on the porch. There's no need for anything more than that."

He pointed his wand at himself and faded into the street behind.

The Owlery.

Of all the places, this.

Severus had never been overly fond of owls, but they were a delight compared to students who'd be here on an early morning during the Christmas break sending letters. And of all the students who might have been sending a letter this morning, it would of course have to be Charity Burbage.

"Good morning, Professor," she said apprehensively, staring at his agitated face.

"What are you doing here?" he snapped.

She stared at him some more. "I'm sending a letter to my mother. And an essay to the Daily Prophet. What are you doing here, Professor?"

Throttling you, if only the universe were just!

He glared down at her and said dangerously, "I don't know why we have to keep going over this, Miss Burbage, but once again I shall tell you that I am not subject to your – you wrote an essay to the Daily Prophet?"

"Yes. I read their opinion piece on safety among one's own kind during war times and thought that their editor could use a quill-lashing." She said this in a peppy, lighthearted tone while fastening her second letter, which looked like "rather a lot" of parchment, as Lily Potter might have called it, to a large brown owl.

Severus rubbed his temples. "What kind of mind-numbing dunderheadedness do they poison your food with at the Gryffindor table? What would convince you that by writing one essay you could right all of the wrongs in this world, Miss Burbage?"

She shrugged. "Oh, I'm not trying to right all of the wrongs in this world, Professor. I'm just hoping that those bigots at the Daily Prophet will read enough of my essay to be forced to confront the fact that they are all a bunch of cowardly fools."

Severus glared at her. "Give me that." He held out his hand and waited. She stared at him defiantly.

"Why?" she asked, and after too long a pause she added, "Sir?"

"Because I told you to," he snarled.

She pried her letter from the owl's claw and handed it to him, the defiance in her face growing stronger as she did.

He set the letter on fire and dropped it, letting it burn and crumple at his feet. She stared at it, and then returned her gaze to his face. "You didn't even read it!" she snapped, which seemed to Severus an odd trifle for her to complain about.

He smirked at her fury even so. It made him feel a little bit better. "If the Prophet had published it, you'd be a target. In fact, if anyone at the Prophet had even started to read it, you'd be a target. Don't be an idiot, Miss Burbage."

"I'm not afraid of You-Know-Who!" she yelled after him as he swept from the room.

"Yes you are," he muttered.

"Go over it again," ordered Lily sternly. "What did you say to him?"

"I TOLD you," James replied irritably, "I didn't say ANYTHING! He just forced me to talk to him on the porch and then he lost his mind!"

"Well, what was he saying?" Lily asked.

"He was talking about Hogwarts," James replied, somewhat evasively.

Lily raised her eyebrows at him.

James relented. "Lily, you know that I – well, I'm not – proud. Of course I'm not proud of the way that – but I never became a Death Eater. If we're prepared to trust him knowing what he's done, knowing that he worked for Voldemort, then why can't he get over what happened when we were both kids?"

Lily sighed. "I think he can, James. But maybe he can't… like you. He can ignore that he doesn't like you enough to keep you alive, but maybe he just can't be your friend. He isn't the most flexible of people, you know."

James looked at her intently. "You were his friend once, weren't you?"

She raised her eyebrows at him again. "I thought you already knew that."

"No. We all thought you had a self-destructive fondness for him, the same way that you always liked Mrs. Norris. And that you were using him for Potions tips."

Lily snorted. "You four never could just accept the fact that I brewed better potions than you."

"Or that you could hang around that close to Snivellus risking nausea just for the heck of it," James added helpfully. Lily glared at him. "Oh calm down, I'm just messing around, Lily. So. What happened?"

Lily opened her mouth but said nothing; faint notes of the "Magic Music Moose" song Harry had written floated through the floor from his nursery. They listened until he stopped singing again.

"He insulted me," Lily said simply. "Called me 'Mudblood'."

James popped a chocolate frog into his mouth. "Oh yeah, I was there for that," he said flippantly while he chewed. "You're telling me he never called you that before?"

"Never."

"So… when he came crawling back to you…."

"He came to apologize almost immediately. But I'd had enough. It wasn't just that he lost control, it was that he had to keep that control in the first place. He was set on the path to becoming a Death Eater, so why should I have bothered? There's only so much disappointment you can take from one person."

"I guess so," James said uneasily, staring down at his hands.