Tumblr prompt from truelondonsoul: "Sherlock accidentally makes a potion or something and turns into a cat and meets Toby. Molly doesn't know what happened." I decided to go Potter!lock.

It both amused and irritated him to admit that he frankly had no clue what had just happened. He had been in his dorm, alone and sitting in the middle of the room with a cauldron stationed in front of him and frankly, everything had been going swimmingly.

Well, right up until he added the wolfsbane, that is. Now, he was lying on the floor with a neon blue mist floating above him. And somehow, he felt lighter. That too, was strange. Just exactly what had happened to him?

Carefully, he stood. Even his feet felt lighter; softer. He looked around for a moment. However strange his body felt, it seemed that his senses had benefited from the accident most of all. Everything he felt, heard, saw and even smelt was sharper; crisper.

Idly, he called for John. But when a sharp mewling sound emitted from his throat, he jumped back—and straight into the eyeline of Anderson's mirror.

A low, drawn out meow poured from his throat as he groaned and curled up inside himself. He, Sherlock Holmes—the genius of Ravenclaw House—had somehow turned himself into a cat.

A very handsome cat, with smooth black fur and sharp blue eyes, but still a cat all the same.

Molly, he thought. She'll be able to help. It was with that thought that Sherlock got to his feet—paws—and padded out of the boy's dorms and slipped across the corridor towards the girl's dormitory.

When he got there, he found it to be empty, which was annoying. He assumed that Molly would be cooped up on her bed like she always was on her days off, with her nose stuck in one of the many textbooks she kept beside her bed. He huffed, but that was stopped by a sudden yawn/yowl. How could he be tired already? It was barely noon, for Christ's sake! Or was accidentally turning into a cat really this physically draining?

It was no matter. He stared up at Molly's bed for a long time, calculating the jump. When he was satisfied, he rested back on his hind legs—whilst desperately trying not to think about the fact that he now had hind legs—and jumped.

It turned out cats were a lot stronger than he thought, and he sailed through the air, coming to a collision with a soft, bouncy pillow. He meowed in surprise and rolled away, hitting something else that was soft; but not nearly as bouncy.

"You're better than tuna…" a voice said sleepily. Curious, Sherlock raised his cat head and looked to see that Toby, Molly's furball of an animal, was what had broken his fall. So apparently his transformation into a cat had enabled him to understand cats. Wonderful.

Toby however, had barely noticed Sherlock's weight on him and had continued sleeping. Grumpily, Sherlock butted his head against Toby's back. Immediately, Toby jerked awake and rolled over to glare at the intruder.

"Who are you?" he said shortly, curling his paws closer to him. Sherlock looked down, uneager to engage in conversation. This day was already weirder; he wasn't going to let it get even more so. Claws retracted, Toby swiped at Sherlock's ear.

"I said, who are you? What are you doing on my human's bed?"

"Your human?!" Sherlock cried, indignant. "She's Molly Hooper, not just your human!"

Toby's eyes narrowed. It was almost as if he were frowning. "You're weird."

"I'm not weird! I'm Sherlock Holmes, and I—" He stopped, curling back against himself as Toby aimed an inquisitive look at him.

"What happened to you?"

"Accident. With some wolfsbane."

"Oh," was Toby's only reply as he closed his eyes to resume his sleep. Sherlock repressed his own urge to sleep and headbutted Toby again.

"Do you know when Molly will be back? I need her help."

"Yes, I do. And no, I won't tell you," Toby said lazily, flicking his tail slightly.

"Why not?" Sherlock said, indignant.

"Because you like her. And I'm a cat. Cats don't like sharing."

"What does me liking her have to do with anything? You're a cat."

"And cats don't like sharing. I have my human; get your own."

"But I like your human! Very much!" Sherlock retorted, almost whining.

What this conversation must sound like to human ears. Probably like a series of yowls, he mused.

Toby stared, unblinking, at Sherlock for an awful long time.

"Ask her out then, if you like her so much."

Sherlock tried a frown and sat up, his front legs—paws—perched nicely in front of his hind legs (nope, still weird). "You just said…"

Toby yawned and stretched out on the bed. "I don't like sharing my human with people who lie to her. So don't hurt her, or I'll purposely scratch your bed-sheets to shreds every week."

"Um. Okay." Of all the days in Sherlock's life, this was by far and away the strangest.

It was the door opening that caused him to look up. To his relief, he found that it was Molly, and as per usual, she had her nose buried in the pages of a thick hardback textbook. Forgetting himself, Sherlock called her name but once again, all that came out was a short (but loud) mewling sound. Molly promptly dropped her book to the floor and on seeing him, she grinned and sat on the bed. Sherlock nuzzled up close to her, and when she gently scratched and stroked the top of his head, he found that he quite liked it. He made a swift mental note to try and get her to do that when he was back being human.

"Aw. Aren't you a sweetie? I wonder where you came from, hey?" she said as she scooped him into his arms and held him close. She was very warm for a girl of her size. Sherlock snuggled closer and before he knew what was happening, a deep throaty purr was floating out of him.

Molly's fingers froze on his chin as she stared at him.

Uh oh.

Not even a moment went past before Molly let out a large laugh.

"Oh my God! Sherlock!" she spluttered, still unable to contain her laughter. Sherlock tried to glare, but apparently, that only led to another, harder, bout of laughter.

"C'mon, don't look at me like that," she said between giggles. "I didn't transform you into a cat, now did I?"

Sherlock slowly shook his head. Molly sighed lightly and held him close to her once again before standing up. "We'd best get you to Madam Pomfrey—she'll no doubt be able to help you."

Again, Sherlock shook his head. He would already be in enough trouble for even having potion making ingredients in the dorm, let alone concocting a potion which turned him into a cat. Molly sighed again, heavier this time.

"So what do we do? Wait for the potion to wear off?"

Sherlock gave out a small meow of agreement.

"But that could take hours!"

His eyes widened in reply.

"Fine," Molly said after a pause. "We'll go back to your dorm. But if I'm caught by Professor Flitwick, I will tell on you!"

Sherlock said nothing, which Molly rightfully took to mean agreement. Together, they ventured across the corridor and into the boy's dorm which was thankfully still empty. Locking the door behind her, Molly carefully sat down on Sherlock's bed and with him in her arms, they both waited for the potion to release Sherlock of its effects.

It took a little under an hour for him to come back to his normal form. And it was for little under an hour that Sherlock Holmes purred happily in Molly's arms.