Chapter 2: Plotting

Ariadne woke early the next morning to get some studying done in the library before class. She slipped out of her four-poster bed, showered and dressed, trying not to disturb her dormitory-mates. By now, they were used to her strange sleeping and waking habits—coming to bed after late nights in front of the common room fire, and waking at the crack of dawn to polish and revise essays. Her best friend, Sophia, joked that the only candlelit dinner Ariadne ever enjoyed was with a date with Advanced Rune Translation and pumpkin pastieswhile burning the midnight oil. Weirdest of all to her classmates, Ariadne didn't just study to pass her tests. She read Transfiguration Today every night and checked out history of magic books beyond those assigned by Professor Binns. She was currently petitioning Professor McGonagall to add a Theory of Magic course to the curriculum. Ariadne's knowledge of magical theory and history already surpassed those of most fully-qualified, Hogwarts-educated witches and wizards. She intended to become a professor at Hogwarts as soon as she had completed her NEWTs.

The library was deserted, of course. Madam Pince, the librarian, was on very good terms with Ariadne, seeing as she had pored over many dusty volumes students hadn't touched in generations, and always returned her books on time and in impeccable condition. She ushered Ariadne into the library with the closest expression to smiling she ever wore and went back to repairing the binding of an old book.

Ariadne had just settled into her History of Magic notes when she suddenly realized she was not alone. A soft shuffling of papers emanated from the bookcase behind her. She froze, then decided to just ignore it and mind her own business.

But of course, whoever it was wouldn't let her.

"Morning, Morrigan," murmured a voice right by her ear. Ariadne's heart leapt out of her ribcage. Turning slowly and trying to retain her outward composure, her gaze met a dark, brooding pair of eyes, though at the moment they were lit by a spark of amusement.

"Is sneaking up on unsuspecting people who are minding their own business your typical form of greeting?" replied Ariadne, looking back at her notes.

"Only when it's 6:30 in the morning and someone disturbs my peaceful solitude," he answered.

Disturbs his solitude. As though he owned the library. So typical.

Much to her annoyance, Sirius took the seat next to her and set down a stack of creased and dusty books. Ariadne couldn't help but notice the titles of a few. Spells of Illusion and Deception. The Wizard's Guide to Going Unnoticed.

Sirius noticed her looking and leaned in. "Know anything about doubling enchantments, Morrigan?" he asked in a low voice.

"Creates an illusory body double that a witch or wizard can remotely project and control," answered Ariadne automatically.

"Good. Full marks," said Sirius ironically, tilting his chair back on two legs. He said nothing more, and continued perusing Spells of Illusion and Deception.

Ariadne couldn't help herself. "They're also dark magic, and strictly forbidden by wizarding law. Class Three restricted spells."

Sirius merely looked up from his book for a moment.

Ariadne rather too loudly shut her own book. "Black, if I see a double-image of you wandering the castle…"

"Ah, but that's the beauty of it, my love. You wouldn't know it's not me."

"There are ways to identify a double from a real wizard. It's only an illusion, and therefore fallible. And I'm not your 'love'."

Completely ignoring her last comment, Sirius answered, "But they're very difficult to tell apart. Most wizards don't know the difference."

"I'm not most wizards."

Sirius looked up and held her gaze again, as if evaluating her statement. Finally, he closed his book and ever so slowly leaned toward Ariadne.

"Imagine you needed to be in two places at once. Your corporeal form needs to be somewhere to accomplish a very important task, a secret task, involving magic. But you need someone else to think you are somewhere else, to distract them so they don't interfere with this task. No one else can carry out the distraction for you, and no one else can carry out that important magical task, because only you have the skill. It is crucial that everyone else, and one person in particular, be convinced that you are where you're supposed to be."

To her surprise, Ariadne realized she had been pulled in by his intense, silky voice, leaning in closer to hear him.

"A doubling enchantment would be your only choice. Wouldn't you agree?"

Ariadne recovered herself. "It obviously depends on what this important task is. Restricted spells aren't meant to be used lightly."

"Let's assume it's an absolutely critical task. Vital to the safety of Hogwarts castle and everyone in it."

Ariadne narrowed her eyes at him skeptically.

"So what do you think?"

"What do I think about what?"

"The doubling enchantment. Would you lend a helping hand, Morrigan? You say you could tell a weak illusion from a strong one. I'll practice, you'll help me get better."

She knew he was appealing to her pride in her magical skill to pull her into his scheme. But then, maybe he did actually need her help? They were in all the same classes. They competed against each other for the highest marks. Sirius knew what she was capable of.

"So you expect me to risk my prefect status, expulsion, and even punishment by wizarding law, for some harebrained scheme you won't even explain to me properly?"

Sirius sighed and slumped back in his chair. "I knew you were going to say that. Can't even excite you with a little mystery."

"It's going to take more than a little mystery to excite me."

Sirius's eyes glinted, as if he took that as a challenge. "All right, Morrigan. We'll see." And then, infuriatingly, he went back to studying.

Ariadne tried to follow suit, though of course she was burning with curiosity. But she refused to give him the satisfaction of knowing that.

Sirius sighed again. "Shame."

"What?"

"That you'll never get the satisfaction of helping me carry out my important mission."

Ariadne rolled her eyes. He would simply not give up trying to impress her.

"I mean, how else am I going to convince Flitwick that I'm in Charms class while I'm actually…"

Ariadne couldn't deal with it anymore. "Doing WHAT, Black? Spit it out, for Merlin's sake."

Sirius grinned at her. "Sneaking Catherine Whipple out of the castle into Hogsmeade, of course."

A/N: Welcome to my little Potterverse :) I know Sirius/OC fics are a dime a dozen, but I promise Ariadne will be different from any character you've read before! She's a force of nature. I started writing this fic a while ago and just never published it, so I have about 6 chapters ready to go, and I'll post one a day for the next week-ish. Slight warning: content is likely to get more explicit in the coming chapters, hence the M rating. I hope you'll stick around, and thanks for reading!