Disclaimer: I don't own anything. A. N. So... I had no idea this would happen. Hope you enjoy!

Soon they were back home, and Sherlock threw himself on the sofa. Mind palace time, right. So John had said. Before he could add more data to his new mood-smells archive...which he needed to create, actually. Unless he opted to throw something out and replace it with his new knowledge. Decisions, decisions.

Honestly, that had happened to him more often since meeting John than during the entire rest of his life. The amount of details he would have carelessly tossed in the bin and now became suddenly important kept growing. Some day he'd surpass Versailles's size and keep going...and half of it would be John's tastes or John's quips or - John, all over. Awkward. Thankfully, at least, that would stay his secret. One he would not admit, no matter how much the man pushed.

He discovered things had changed a little. It used to be easy to abstract himself and let the rest of the world fade away during mind palace maintenance. Even if John was around. Almost especially if John was around, because he knew nothing bad could possibly happen. Whatever his flatmate opted to entertain himself with in the meantime, Sherlock didn't care. He could obviously deduce it afterwards, if necessary, of course. But it rarely turned out to be.

Now, the awareness of his - of John just wouldn't leave him. Not enough to actively hinder him, luckily. But it was like a low itch that never left him. John was...answering mails, possibly, or writing another stupid blog post, and was pecking at the letters as slowly as ever. And Sherlock knew. He couldn't manage to un-know.

He tried, a few times. Sure, he could work around it, but it didn't mean that he wanted to, if there was another option. But when it seemed like he was close, there was a growl in his head. "Now you stop right there, mister."

Now, Sherlock wasn't new to hosting a lot of people in his head. It would have made sense if it was one of them...especially John, in a way. Sure, it would be annoying, but his brain picking that voice, if part of him was really so keen to hold onto him? He could see it.

No, the weird thing was that it sounded like his own...But not one of his avatars that sometimes still haunted the palace, either. It certainly wasn't his kid self. And the addict, under lock and key much deeper than he currently was, had always been more of a whiner anyway. Cajoling, trying to talk others into what he wanted, aiming for too fast and too confusing to make them see why they should really tell him no.

He couldn't see the source, though, and that was spooky, If his own brain decided to change the rules on him...well, what would be next?

He should have expected it, really. Next time he tried, someone huffed, "I said no. Don't ignore me if you're working on me!"

Hidden below the low table near the sofa, a dark muzzle peeked through. Oh. So he'd gained a wolf self roaming through his mind palace too.

The rules hadn't changed, not much. Maybe he should get it a collar...and a chain. It was one thing to have Irene or Mycroft hiding somewhere, but this...thing surely needed a much stricter control.

He knelt down, materializing a silvery collar in his hands. The wolf backed on all fours, glaring at him all the while. "Oh, come on! Why would you do something like that!"

"Because you don't get to drive. You're already taking too many liberties. Think you can decide how things work? I have news for you, buddy," Sherlock snapped.

"Shouldn't you ask your alpha? You know, before doing something that drastic? What happens if you're knocked out on a case and I can't drive because I'm bound somewhere? That what you want to happen?"

"My alpha?" the detective asked.

"Your captain. Call it what you want. We can be honest between ourselves. It doesn't matter who our sire was. He's been our alpha since before I was in the picture. Who else can get you to listen, huh?"

"It's not like that. I don't -"

"You don't?" the wolf cut him off with a sneer. " What are you doing right now?"

"Because this is his field. I wouldn't argue a diagnosis either. But this palace is mine, and he doesn't get to determine what goes on in here. "

He advanced again, resolved to catch the beast. It had done enough damage, when he'd been on his own, and no innocent blood had been spilled merely because he got lucky. He couldn't count on John to be around every time he transformed, could he? What if next time his instincts woke up and he did something unforgivable?

"Trusting me not an option? Or, you know, trusting yourself?" The wolf shook his head. "What am I asking, that poor thing is still locked downstairs. I'm not a fucking dog, so: back off."

"As if you could actually hurt me. You want an alpha? I'm the alpha of this brain. And a few more letters besides. There's no room at all before...oh, perhaps omicron."

"Before, sure. Now, even, if you want. Don't challenge me and I won't challenge you. I am not looking forward to being in control most of the time. You think you have a hard time dealing with idiots? Try me, and they won't like it. Keep this stupid plan up, though...and see who ends up pinned." The wolf coiled, ready to make good on that promise.

Well, there was nothing for it. Sherlock left the palace. "Jawn! It's not working!"

"What?" his - John asked.

"Mind palace maintenance. A wolf has sneaked in, John. A wolf! And it's a demanding little bitch."

John huffed a laugh. "I have to say, I'm not surprised."

"What is that supposed to mean?" it came out more snarly than Sherlock intended.

John shrugged. "You like having your own way, why would that change?"

"That's the fucking problem! It's not me! It's...it! And it's driving me spare!" Sherlock tugged at his own hair in frustration.

"Now, now. Relax." John sounded so maddeningly reasonable. And once more, the detective found himself wanting to listen.

He groaned.

"What did he do now?" John said, with a little smile.

"He's insane. I am not saying anything more." Sherlock didn't pout. He never pouted

"Well then, how do you want me to help without data? I mean, I could press the issue, but I am trying to be respectful here."

"Point." Sherlock sighed. "It won't go on a leash. But it's not - I can't just leave it wandering around!"

"Why not? He's still you. Well, a part of you at least." John shrugged.

"You're an idiot. And you see, that's part of the problem. It thinks you're its alpha."

"I should hope so!"

The detective tried to loom. It was much more effective with other people. People, thinking about it.

"You're a newborn cub. I kind of expect you to grow into an alpha of your own, and knowing you, quickly too...but for now? I'm here. Not going anywhere. And you will listen to me, when it matters."

"Keyword: when," Sherlock huffed.

"Well, yeah, sure. I'm not too overbearing though, am I?" John looked concerned, and - the detective felt bad about it.

A clear 'apologise' resounded in his brain, which wasn't fair. It wasn't his fault in the first place!

"Of course you're not. But that...thing won't let me ignore you for one second, and frankly, I'm not an actual dog to always stare at you looking for cues!"

"Oh." John actually sounded embarrassed. "Ok, change."

"What?"

"Change. Yes, there are other ways we could do this, but I'm trying not to overwhelm you with too many new details at once. If you want me to fix it, let me." John went and shifted himself, looking up at him with a patient stare.

Well, what was the worst that could happen? John wouldn't let him make a mess. With a sigh, Sherlock pulled the wolf to the forefront.

The wolf whined, and rolled over.

John lounged at his side, nosing at him. "It's okay. I'm sorry." Not in English, but the message was clear anyway.

Sherlock rolled over again, one side touching him. His head tilted in confusion.

"I should have known you'd be anxious. Getting changed, and then a case, and then lessons... I never really got you settled, did I?"

"I'm fine."

"You will be. You don't need to be on alert all the time, puppy. Have a nap. Let him be - him. Still you, I know, it's just... It'll take a little getting used to. It sure did me. You know I will look out for you, don't you? All of you."

"I know." Sherlock's tail wagged weakly.

"Well then, if you're needed, I'll get you. Promise. Until then...I'm not that interesting."

"Wrong."

John huffed a laugh. "Maybe. But you don't have to pay attention. Relax. And let him relax, too.

"You...want me on a leash?" The poor pup looked entirely miserable.

"I'm trying to avoid that. Leave it all to me, okay? No stress. Stress is bad. Breathe. I've got you."

The wolf whined.

"Would I lie to you? Keep quiet, yes. Outright lie, no. And I don't even need to lie, not anymore. So... it's your choice. You either trust me, or you don't."

"I doooo." The black tail wagged softly.

"Then, you know what to do."

The black wolf nosed at his shoulder, before changing back.

John grinned at him, in wolf form, and kept doing it while he turned back.

"That was all?" Sherlock didn't seem impressed.

"What were you hoping for, exactly?"

Sherlock glared at him. He didn't have an answer to that.

"Why don't you go back to your mind palace, and then we'll see if we have further complaints?"

That was unarguable. Sherlock went back to the sofa, rolled over, giving his back to the room, and tried again. Hoping he hadn't lost the data in the meantime. That would have been embarrassing.

This time, things were normal. Suspiciously normal. No hint of the outside in his brain. No extra guests being loud, or visible, or anything. Part of him was tempted to find him again, and make sure things would stay that was. But that would mean getting distracted, twice in one afternoon, and he'd really misplace the data if he did.

First thing first. Archiving what he'd learned. After that was done...well. He could go looking for his new tenant.

He ended up creating a whole new room for wolf data. If, besides the cabinets, there was a dog bed...well, it wasn't a dog, sure, and it'd been vehement on the matter. But if it ended up attracted to its (hopefully) den, it would make trapping it all the easier. Maybe he should add a toy or two, too?

Nah, that would be too obvious. And possibly humiliating. He needed to be smart about this. He'd show the mutt who the actual Sherlock Holmes was.