I've never been satisfied with the original epilogue, so this is an alternate ending that could replace the last chapter.
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It was ten o'clock at night. There should be nobody knocking outside his office at this hour…
"What?" Snape growled, without opening his door. "It's after curfew. I'll give you one chance to escape before I see who it is…"
"It's me, Professor. Prefects don't have curfews, remember?"
Muttering under his breath, trying with all his might to appear annoyed, Snape went and jerked the door open. "Miss Potter, do you realize what time it is? Very well, come in, sit down."
Sophie brushed by him, flipping her sixteen years' worth of hair behind her shoulders and making for the armchair closest to the fireplace. As usual, she got right to the point. "Professor, I'm nervous."
He settled into a chair next to her. "Nervous?"
"Don't tell me you didn't know tomorrow is the day."
Snape shrugged. "Of course I knew. I'm surprised you remembered. Is that what you're nervous about?"
"Oh, excellent insight, sir - five points to Slytherin." Her lip curled in a sneer almost as effective as his own. "Professor, Lucius Malfoy has been in jail - in Azkaban - for five years now. And starting tomorrow he'll be out. And once he kisses enough backsides in the Ministry, I'm sure the rest of the Dark Circle will get out, too. To put it mildly, I would guess that he's still really angry at me. He may be an old geezer, but he's a powerful old geezer. Of course I'm nervous."
"Excuse me. Geezer? Miss Potter, I'm almost as old as Lucius myself."
Snape certainly knew how to push her buttons. The nonchalance in his tone made her almost frantic. "Quit it! Don't tell me you aren't nervous, too, sir. I…he…"
Realizing that he couldn't allay her fears by delicately suggesting to ignore them, Snape had to resort to more direct means. "Lucius and his friends have been after my blood since before you were born, Sophie," he said softly. "I've started to think their power is overestimated. You're certainly safe here at Hogwarts." When she didn't answer, he pressed, "What are you worried about? That they'll storm the castle? Or that they'll go after your parents? Because I'm sure the ancient magic of Hogwarts isn't powerful enough to fend off a few disgruntled old convicts. And I'm equally sure the Famous Harry Potter hasn't set up an obscene amount of powerful wards all around his home for protection…"
His sarcasm made her grin ruefully. Maybe he was right. "I guess so. I'm just…I don't know, I'm afraid for me and Julien. I mean, I know the castle is safe and all, but still. I just don't like the idea of a bunch of evil nutters free and hoping to kill me."
Snape arched an eyebrow. "I assure you, you'll get used to it," he said stiffly. "It only took me about three years." Seeing that she was taking him seriously, he sighed and conjured them both hot chocolate. "Calm down, Miss Potter. I'm not happy about it either, but I assure you, nothing will come of this. Half the Circle has gone insane in captivity, and none of the survivors will risk another stint in Azkaban lightly."
She sipped her hot chocolate. "I guess."
Sensing that she was still not comforted, he tried one more thing. "Just be on your guard, and if you do see anything suspicious, you know I'll always be here, resident dungeon-troll and all-purpose-Potter-Saver. You...and your brother, I suppose...are welcome to come to me if you feel anything is the matter."
"I thought you told Dad you were through with rescuing Potters," she said, mood lightening a little bit. Snape was stirring marshmallows into his hot chocolate, and as he reached out to put his cup back on the table, she was suddenly struck by how graceful his movements were. "You know, Professor," she said absently, "I think if I were sixty years older I'd make a pass at you."
They both froze, equally shocked by her comment. He recovered first. "You'd be robbing the cradle, Miss Potter," he said silkily, "As that would put you at seventy-six and I'm still in my fifties." After a short pause, in which she giggled through her furious blush, he murmured, "James Potter would turn over in his grave if he could hear his granddaughter say that." He, too, seemed on the verge of laughter.
She ducked her head to prevent eye contact. This, however, made her hair tumble down into her cocoa. While she grumbled and fished a few strands out, Snape sent a spell at her and the rest of her hair suddenly began to braid itself into a long neat rope. "Hey! Not again…"
The Professor was almost smiling…that is, until Sophie mumbled something under her breath and a jet of light shot from her sleeve.
Caught totally off guard, he completely failed to dodge her hex, and wound up with two short braids that made him look rather like Pocahontas.
"Miss Potter!" he breathed, outraged. Had she not trusted her smile's ability to charm her out of trouble, she might have worried that she'd crossed a line. As it was, though, she just grinned sweetly and told him she thought the look was stunning.
His glare persisted until she conjured him a mirror, at which point his face underwent a strange contortion she recognized as the suppression of laughter. After waving his hand to undo the spell, he warned, "One day, you will push me too far."
"I don't know, sir…I think I've heard enough stories to learn from everybody else's mistakes… the rules are…let's see… don't try to turn you into a werewolf, don't set your robes on fire, don't melt any more cauldrons in your class, don't make fun of your nose or hair, don't ask you to spy on any more evil wizards, don't have a scar on my forehead, and preferably don't be related to someone who does. Have I missed anything?"
His eyes were wide. "I see that I have failed miserably where intimidation is concerned," he said finally, with a hint of ironic amusement in his voice. "I must ask you not to share the secret of your courage with anyone else, or I shall never be able to conduct a successful Potions class again."
"Your secrets are safe with me, sir," she said, but the honesty in her tone was offset by a mischievous gleam in her eye.
He rose and steered her towards the door. "Go to bed, Miss Potter. And don't worry. I sincerely doubt you have anything to fear."
She nodded. "Okay. Thanks, Professor. Really." As his office door opened, they caught sight of a shadow lurking in the corridor.
Snape grinned nastily. "Five points from Gryffindor, Mr. Potter, for being out after hours. You, at least, are not a Prefect."
"-for which we heartily thank the Headmaster's wisdom," Sophie muttered, but nevertheless indulged her brother's complaining all the way back out of the dungeons.
Standing in the corridor until their footsteps died away, Snape fought a smile as the boy's whines filled the cold air. "- still a mean, slimy old toad, Sophie. Really! Like it's a mortal sin to escort your sister back to her tower. I wish I knew a good greasy old hex…"
Some things would never change.

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THE END

So. What did you think? I'm not sure which ending I like better. I kind of think Snape is too much of a jerk in the other one, but he might be too nice this time around. Could you guys please review if you have an opinion? I think I'm going to delete whichever ending nobody likes. Thanks for reading.