Hermione Granger sat in a squishy armchair in the Gryffindor common room, cutting parallel holes into a white sheet. Her attention was solely dedicated to this task, not rain nor sleet nor snow nor silly little poodles who escape their leashes could distract her from cutting two parallel holes into the white sheet.
Several minutes after she started, Harry and Ron walked into the common room.
"Hi, Hermione!" they chorused cheerfully. They were both red-faced and happy, having just finished a successful Quidditch practice.
Hermione immediately stopped cutting. "Hi, guys. Have you started your costumes yet?"
Harry and Ron shared a confused look. "Costumes for what?"
"You know, your costumes, for that thing called Halloween tomorrow?"
"Hermione," Harry said in a patient tone, "there's no reason to have a costume for Halloween. We don't have trick-or-treating or anything of the sort. All we have is a feast, and I'm pretty sure we're required to wear our school uniform to it."
"Oh, honestly. Do you two ever pay attention?" Hermione demanded in a huff. "The Headmaster announced that we were going to have a Halloween Costume Ball nearly three weeks ago."
The two boys looked rather badly startled, especially Ron. "I guess we must have missed that one, Hermione—"
"Ron, I asked you if you wanted to go with me to the dance last week and you said yes! What planet are you on?"
"Earth?" he offered blankly, then immediately regretted it when Hermione gave him a glare that would have cowed Snape. "Er, I mean, of course I remember and I was just about to run upstairs and grab a sheet so we could be matching ghosts. Wait right there." He then ran up the stairs to the boy's dormitory, leaving Harry to face Hermione.
"I don't think I'll be going." he admitted. "I'd rather just stay here and polish my broom or something."
"But Harry, think of the fun we could have! You could dress up in a costume that covers you scar, then no one would know you were you! You could have a whole night of just being a normal person. Isn't that what you've always wanted?"
Harry smiled gently. "No, Hermione, it's okay. I've had enough of balls for a lifetime, if you know what I mean."
He was, of course, referring to the Yule Ball in their fourth year.
"Well…All right, then. If that's what will make you happy." Hermione hedged finally.
"It will." Harry said reassuringly.
THE NEXT EVENING
Hermione the sheet-ghost met Ron the sheet-ghost in the common room. She got down to business immediately.
"Where's Harry? Could you convince him to go at the last minute?"
"No, he went to the Room of Requirement to relax."
Disappointed by Harry's absence, but determined to have a good time anyway, the young couple made their way to the Great Hall for the ball.
In an abandoned classroom elsewhere in the castle, a teenage boy straightened his meticulously-maintained Gryffindor robe, making sure the crest was visible. He then brushed his messy black bangs to the side, revealing a thin lightning bolt scar. He adjusted his slightly-too-big glasses for the third time and made his way out of the classroom and towards the Great Hall.
In the Great Hall itself, the student body in general was having a good time. They seemed to mostly be in a mood to forget the house system for a night, especially considering that some students were in costumes that covered their entire bodies, making identification difficult.
A skinny, pale, black-haired boy in Gryffindor robes slipped in and out of the crowd, apparently looking for a specific person. He tapped Dracula on the shoulder and was rewarded with the inquiring face of Draco Malfoy. His face switched from curious to furious comically fast as he spat out "What do you want, Potter?"
"Excuse me?" the boy demanded, obviously startled and a little indignant. "What are you on about—oh. Right. It's the costume, isn't it?"
"You aren't wearing a costume, Potter. I can see you have all the intelligence of a rotting piece of wood, as usual."
"No, no. This," he gestured at himself, "is my costume. I'm Harry Potter. Good, right, Malfoy?"
Draco's face flushed. "Oh, sorry. You look just like him." Then, in a hushed voice—"Did you use polyjuice?"
The boy smiled airily. "Oh, something like that. I just wanted to say hello. Enjoy the dance, eh, Malfoy?"
"Sure, you too. Sorry again!" Draco called as the boy slipped back into the crowd.
The boy worked his way through the crowded dance floor, chatting and joking with everyone he came across. The students seemed to be getting a kick out of his costume, and he was enjoying himself immensely.
After an indeterminate time, the boy found himself casually enjoying a glass of punch next to Severus Snape. "Evening, Professor." he said politely.
"Don't talk to me, Potter. Your disease is catching." the older man sneered.
To Snape's surprise, the boy laughed lightly. "You'd be amazed how often I've been getting that tonight. It's my costume, I think."
Snape's face took on a startled look. "You're not—"
"No, sir. Well, I am for tonight. I heard rumor that the real deal isn't even in attendance."
Snape couldn't help but grin slightly. "Five points to whatever house you belong to for a witty costume."
The boy inclined his head. "Thank you, sir."
They stood side-by-side in companionable silence for several moments before the boy moved back into the throng.
By the end of the night, the boy had socialized with nearly every person in the school and had even been invited into the Hufflepuff common room for a game of gobstones, which he had lost spectacularly, but had enjoyed immensely.
Finally, tuckered out from a night of fun, the boy ducked into an empty classroom, slipped a shimmering cloak around himself and disappeared.
Ten minutes later, Harry Potter stepped into the Gryffindor common room.
He was immediately greeted by Ron and Hermione.
"Oi, mate, you missed a real good time." Ron said enthusiastically. "There was even this guy dressed up as you. He must've used a glamour charm or something—we actually mistook him for you at first. Didn't we, Hermione?"
"Yeah. Sorry, Harry." Hermione admitted with an embarrassed laugh. "Well, I guess you don't want to know about a dance you didn't even want to go to. What did you do tonight?"
Harry beamed at the two of them.
"Oh, not much. I just pretended to be a normal guy for a night."