Disclaimer: The characters of Supernatural do not belong to me. The original character of Allegra does.

A/N: So, in all likelihood, my story Seven Days is dead.

I just seem to have lost steam on it. I'm sorry to those of you who were reading it regularly, but I just lost the love for it. I may pick it up again later, but this story here bit me hard and wouldn't let go. This one I will continue, as I have other chapters planned for it, but it's a bit complicated. I've always wanted to do a Harry Potter/Supernatural crossover story, but I didn't want to do anything that was cheesy. I then wondered about Sam and Dean having a sister they didn't know about who went to Hogwarts, and this unfolded out of that.

My favorite character from Harry Potter is Remus Lupin, but a very close second is Severus Snape. So Sam and Dean's sister in this story was raised by him. The background is given in this chapter in as simple a way as I can do it without making it overly simplistic. Warning-Dean is a jerk to Allegra in this chapter and probably the next, but I don't plan on leaving that for too long.

Also, yes, I did name Allegra after my allergy medication. It is allergy season where I live, and without my Allegra on hand I think I would simply fade away and die (dramatic, I know, but the pollen levels are sky high right now, making me grouchy and sick).

Anyway, everyone enjoy! Stay safe and stay healthy!

There were times Dean Winchester swore that his sister was a statue.

His sister. His very, very British sister. Complete with accent and everything. Nope, it never got less weird as he said it.

Bobby had told Sam and Dean about her two weeks earlier. Dean would never forget that conversation. He'd come to Bobby's to find a little girl, maybe nine or ten, sleeping on Bobby's couch. Bobby had chastised him for coming in the house loudly, then pulled him in to the kitchen and sat him down for a 'chat', before giving Dean a letter from, of all people, his father.

His father that had been dead for more than two years now.

Dean,

This is going to shock you, maybe even more than it did me when I found out. I hoped by some miracle that you never would have to find out, but I guess here we are.

She's with Bobby because something's happened to me and I'm not able to take care of her. If she's over the age of ten, then she won't be staying with you for too long. Once she turns eleven, she'll head off to a special boarding school every school year and will only need a place to stay in the summertime.

I've left enough responsibility on your shoulders, Dean. I know you could handle taking care of your sister, but now that Sam is almost grown, Bobby and I agree you need a break from having to raise a kid. He will take care of your sister if need be during summers and her breaks from school.

I'm sorry, son, I wish I could be more specific with you about what's going on, but this is your sister's story to tell. Not mine.

Dean, you and her are like oil and water. Your sister may seem a bit…stiff…but she's a great kid. Just be nice to her and try to get to know her. Do that for me, Dean. Please.

I know you won't let me down.

-Dad

Dean sighed. The house was entirely too quiet for someone else to be there. Sam and Bobby had gone out to find something for the hunt Sam and Dean were about to leave for, leaving Dean alone with Allie-sorry, as she insisted, her name was Allegra-in the hopes that the two of them could come to some sort of 'understanding', if not start the 'beginnings of a friendship'.

Sam's words, not Dean's.

Allegra sighed quietly and continued to ignore Dean, writing carefully her letter to her father. She knew that Dean didn't trust her, though he'd not been foolish enough yet to say it out loud. She didn't blame Dean for the mistrust. She didn't have a great deal of it for him either. Bobby had earned her trust years before, when she'd first met him through her beloved uncle Jo on a trip to visit him for a couple of days. At first, she'd avoided the man, but warmed up to him quickly when he fixed her a treat she'd never had before and come to love ever since.

Rice Krispies. They were now her favorite sweet.

When her father had told her, just over a month ago, that she would have to leave to stay with friends of her uncle Jo's for a while, she'd been thrilled to find out that it was Bobby. But, her father cautioned, she likely wouldn't be alone there and had to do her very best to be on good behavior. If she wasn't, he warned, then when he saw her again, she'd be in big trouble.

So, through all the times Dean had stared at her, snapped at her, or called her that ridiculous nickname which she expressly forbid the use of-Allie, even the thought of it made her cringe-she had been on her best behavior.

Dean seemed to have an interesting weakness. She seemed to be able to annoy him the most when she was exceptionally kind to him. So Allegra went out of her way for Dean. She cooked for him, asked if she could help him with any chores, asked so politely that he call her by her actual name that even her normally stone faced father would have proud, and wished him a good morning and a good night every day that he was at Bobby's. It seemed, and Sam agreed with much laughter, that treating him kindly gave him nothing to complain about, which just made him more annoyed.

And oh, how Allegra loved annoying her older brother. Especially when there was nothing he could do about it without looking like a fool.

Sam was different. At first, Allegra didn't trust him, just as she didn't trust Dean. But that quickly changed. The second night Allegra had been at Bobby's house, with Sam sleeping upstairs, she'd woken up from a nightmare wanting her father. Sam had apparently heard, and knocked on her door to check on her. He'd ended up holding her that night until she fell back asleep, not being the least bit bothered at being woken up in the middle of the night. Since then, she and Sam had bonded over their love of books, each sharing stories from their own respective worlds.

Allegra was used to skepticism. Being raised by Severus Snape, it came to her without a bit of effort on her part. What puzzled her the most about Sam and Dean's differing attitudes to her. Dean, who knew next to nothing about the wizarding world, didn't trust her a bit, no matter how much she tried to prove to him that she was just a normal girl. Sam, who knew the most about the moment about the wizarding world, due to an extensive discussion the two of them had had about it, seemed to have complete faith that she was a good person.

So why did Dean continue to look at her like she was a bug?

She would never admit to anyone, much less Dean, that the way he looked at her and acted around her bothered her in the least. But it did. So, when Sam and Bobby had left earlier in the day, she'd begged Sam to let her go too, only to be met with a plea from him to get to know Dean.

"Please just try for me, Sis."

Reluctantly, she gave in, but decided she would let Dean lead the charge now. She sat at the table and for a long time, stared at a photo that contained the one thing in the world she and Dean shared in common.

John Winchester.

Allegra had somehow figured the story out on her own when she was just five years old. John Winchester was her birth father, Severus Snape her uncle and adopted dad. Not wanting to burden her mother with the knowledge that Allegra knew, she'd asked her uncle Jo why the adults had hidden this from her the next time he came to visit. Much to her dismay, her uncle told her mother and father that she knew, and Mummy told her the whole story so that her five year old brain could understand it.

When Mummy had been just twenty years old, her mother, Allegra's grandmother Eileen, had died. Mummy and Granny had planned to go on a trip to America, but the trip was postponed when Granny died. Mummy had decided to go anyway, and there she'd met a handsome American named John Winchester. Knowing that she'd have a hard time fitting in in America, she'd immediately come back home and moved in with her brother, and Allegra had eventually started calling him Daddy. Mummy hadn't had the heart to correct her, but wanting to be honest with John, she'd sent him a letter. They'd agreed that since John wouldn't be able to visit often, it was better that they let her think her uncle Severus was her Daddy, so she'd always have a father around, and that John would be her uncle instead.

Allegra remembered that conversation clearly. She hadn't been angry about her parents and uncle not telling her. She understood, even then, that there were some things she was too young to know. This was probably one of them. But she did know it, and she felt bad for her uncle Jo that he didn't get to be her Daddy. So, sitting on that bench outside their home at the time, her mother and father seated on the left of her and uncle Jo on the right of her, she'd looked at him and asked the question that would seal her family forever in her mind.

"Will it make you sad if I don't call you Daddy?" Allegra had asked. "I still love you, but you don't feels like my Daddy."

She saw the sadness in her uncle Jo's eyes, but he'd smiled quickly to try and hide it. "No, sweetness. It won't bother me. You're better off here with your mom anyway."

Allegra had simply nodded, hugged all the adults sitting there with her, and jumped off the bench. She convinced them to play a ball game with her, and the conversation was put behind them for a few more years.

Then the worst came.

Rebecca Snape had died in her sleep early on the morning of Allegra's ninth birthday. There had been no cause found, neither by the wizarding world or the muggle doctor that Severus had eventually taken her mother's body to. She seemed to have simply stopped breathing, and the cause remained a mystery. Her uncle Jo had come for the funeral and stayed for a few days, helping her father adjust to life without Rebecca. It was during that week that she'd found out another Big Truth of her life.

She had two brothers.

But in the wake of her mother's death, she simply didn't care. Allegra was angry for what felt like a long time. Angry at her mother for leaving her. Angry that her father grew distant and didn't seem to want anything to do with her. Angry that for some reason, her mother's breath had been stolen from her body and no one seemed competent enough to figure out why. Angry at her uncle Jo for leaving her when he did.

Eventually, the anger faded, but it still simmered beneath the surface.

Now, Allegra simply had to deal with whatever came her way. Overall, the trip to Bobby's hadn't been as bad as she'd thought it might be, with Dean being the big exception. She knew the trip wasn't forever, as at the end of the summer, she'd be attending Hogwarts School of Witchcraft and Wizardry and would be back again in familiar surroundings.

If only she could get her letter.

It was July already, and she knew from past years with her father teaching at Hogwarts that every student had to send a return letter back by the end of the month in order to be accepted. She knew that Severus had sent her here to keep her safe from something, but surely he didn't mean for her to be here for good. He simply hadn't withheld her letter from her, forcing her to continue going to muggle school.

Had he?

When Dean cleared his throat for the fourth time, Allegra broke herself out of her chain of thought. Dean wanted something and was either too annoyed or, to her unending amusement, too afraid to ask her. With as much self-control as she could muster, wiping away a tear as she took another look at the photo of her mother, Allegra answered back,

"What is it, Dean?"

"I was just seeing if you wanted some lunch."

"No thank you." Allegra said without looking up at him.

"You sure?"

"Positively positive." Allegra said again, gritting her teeth. She absolutely hated answering the same question twice.

Dean, annoyed, snapped at her again. Sam wouldn't like it, but he didn't care. "Look, I'm just trying to be nice to you…"

"Only because your brother made you." Allegra answered, coming as close to arguing with him as she'd ever truly come. "What have I done to you, Dean?"

"What have you done? You're a…a…"

"I'm a what, Dean?"

"You know, you're a…."

"A witch? Is that your problem with me? Witch isn't a bad word, Dean. There's millions of us all around the world."

Dean's eyes grew huge.

"Yeah, that's right. Millions. And if you're not gonna trust all of us because of the actions of a few witches you met in the past, that makes you nothing but a bigot, Dean Winchester." Dean opened his mouth wide to refute, but Allegra continued with a fury. "When I was five years old, me mum brought me out to a muggle town to see a show. We were robbed on our way back home. How would you like me to judge you based on the actions of that one muggle? Are you a thief, Dean?"

"What, no?"

"Why wouldn't you be? That muggle was. Surely all of them are."

Before Dean could say anything back, the front door opened and Sam and Bobby stepped back inside. Allegra wiped her face again, not wanting them to see her crying. Sam and Bobby were doing their best to make her feel at home and welcome, and she thought it rude to let them know she was sad. But all those thoughts were driven from her head.

Sam and Bobby had brought another person back with them. Standing in the middle of Bobby's living room, looking in at her with a rare smile on his face and a bouquet of her favorite hyacinth flowers in one hand, was her father. Her tears of misery from just a few moments before immediately changed to tears of complete joy.

"I believe the proper greeting…"

Severus's words were said with a drawl that was answered before he could finish his sentence with a completely undignified squeal of delight from Allegra. She knocked over Bobby's kitchen chair and ran to her father so hard she nearly knocked him down.

"DAD!"

"Oh, hello, darling. I've missed you so."