A/N I have decided to change the rating to T because I have decided there will be some cursing in this story and in addition to that idk how this is gonna progress since I'm writing about two angsty bois.

Sirius opened the door to Regulus' room, not bothering to knock. Almost a week had passed since he had seen Harry, since their fight. They hadn't talked much, other than Regulus telling him they should go on at least one walk a day. As much as he loved the freedom he felt going on walks, a part of him rebelled at the idea of being told what to do. Besides, he hadn't been able to go looking for Harry or Peter since last week. He had to find Peter before the school year started, it would be harder to kill him after. They would be guarding Hogwarts well, not that Sirius couldn't get around them, he was a marauder, he could do anything!

It took several moments of staring at Regulus' empty room before Sirius realized that it was empty. That was strange, Regulus used to always be in his room, and even after their fight he always told Sirius when he was leaving. He shut the door and started down the stairs.

12 Grimmauld Place was an interesting building. When he was a teenager he had wondered why his bigoted parents had chosen to live in a house surrounded by muggles on every side. Somehow, despite being built by muggles, the house seemed to capture the very essence of the black family. On the surface it looked elegant, riegel, and old, but under the surface it was suffocating. Not only did every wall have something gruesome on it—portraits, stuffed heads of long-dead house elfs, the tapestry—everywhere you turned was evidence of dark magic.

The memories didn't help.

He stuck his head into the drawing room, but it too was empty. Something thumped against the ceiling. Sirius winced. That was Father's study. Why would Regulus be there? He ran up the stairs, stopped in front of the study door, and took a deep breath. He was about to open the study door, without knocking, but the sound of Regulus' voice inside stopped him.

"I could write to Karkaroff, ask him if his library has more information. Of course then he'd know," Regulus said.

"Kreacher could go to the library and look for Master Regulus."

"No, crossing international borders without a permit is risky, even for a house elf."

Sirius opened the door.

Regulus looked up sharply, slid something off the desk into one of the drawers, and closed the rather large book he had been reading, all within seconds of Sirius opening the door. Kreacher, who had been standing bright by the desk shrunk back towards the corner

"Why are you in Father's study?" Sirius asked.

Regulus' expression was guarded, almost fearful, just like it had been right after Sirius ran away. "It's not his anymore, it's mine. I own the house, and he's dead," Regulus said.

"What are you working on?" Sirius asked. A small thread of anger started to wrap itself around Sirius. Even now the dark arts had Regulus trapped.

"It's not important," Regulus snapped. "Do you need something?"

"I need to find Peter," Sirius said, "but clearly all you care about is whatever dark magic you're playing with now."

Regulus' expression hardened even more. "And how do you expect to find a rat in the entirety of Great Britain and Ireland?"

Sirius rolled his eyes. Did he have to spell everything out for him? "I don't have to find the rat, I just have to find the boy that's got the rat!"

"What's his name?"

"I don't remember, he was in the prophet."

Regulus turned towards Kreacher. "Kreacher, bring me the Daily Prophet from every day in the week leading up to Sirius' escape," he said.

"No, it was ten days before I escaped," Sirius said.

"Never mind Kreacher, just bring the prophet from ten days before Sirius escaped."

Kreacher disapperated.

Silence followed the sound, and it wasn't a comfortable one. It was just like it had been before. Sirius clenched his jaw. A small part of him had dared to hope when Regulus had let him stay that all this might finally be behind them, but here was proof that it wasn't.

"You're still experimenting with dark magic, aren't you?" Sirius said.

"If you hadn't noticed, the house is filled with dark magic and cursed objects, I couldn't avoid it if I tried," Regulus said, his voice flat.

"I know, but…"

A loud knock on the door interrupted Sirius, and something akin to panic flashed through his mind.

"Dog, now," Regulus said. He stood up and walked past Sirius.

Sirius followed him in dog form down to the front door. The person knocked again. They seemed to be using a very specific pattern, the one Moody had used when they were out as Aurors. But why would Moody be here? He had retired, hadn't he? No one else knew the pattern, even Sirius and James working together hadn't been able to figure it out.

Mother was muttering something from underneath her curtains, but Sirius didn't care enough to listen. Instead he watched intently as Regulus opened the door.

It was Andy's kid, this time with curly light brown hair, and that Auror that they'd met the day he saw Harry.

"Can I help you?" Regulus asked.

The Auror, whose name Sirius thought was Harrison, looked extremely pleased with himself. "Good afternoon Mr Black. We have official permission from the chief warlock of the wizengamot to search your house for any indication that you might be harboring Black," he said.

Sirius looked at Regulus. If it was possible, his expression seemed even more closed off than it already was. He looked at Auror Harrison, then stepped aside. "You're welcome to look around, I have nothing to hide."

Auror Harrison walked in, followed by Andy's kid. "Mx Tonks will be joining me today as part of their training," Auror Harrison said.

"Did you name your dog yet?" Tonks asked, seemingly taking her name being said as an invitation to speak.

Regulus seemed to freeze for a second. "I've been calling him Canis Major," he said. "Canis Minor when he chews up my shoes."

Tonks laughed and Sirius couldn't help a little growl. Of course Regulus would give him a stuffy astronomical name with a built in insult.

"It's alright boy," Tonks said, moving closer to Sirius and petting him. "All the best blokes have stuffy names."

Sirius wagged his tail. As humiliating as it could be to let people scratch his head, it felt really good.

"We're not here to play with the dog, Tonks," Auror Harrison said.

Sirius laughed, which came out as more of a bark. He really didn't like Auror Harrison.

Regulus followed Auror Harrison closely as he walked through the Hours, trying to think of anything that indicated Sirius' presence. They had been careful not to draw any attention to themselves, but clearly not careful enough. Honestly he should have expected Auror Harrison to find an excuse to search the house, he had never hesitated to make it clear that he was suspicious of Regulus. During the war Father had insisted that they had to be prepared for a ministry search at any time. Regulus hadn't paid too much attention to that, after all, keeping a collage of newspaper clippings about the Dark Lord wasn't exactly subtle. Now he understood. Even just one thing indicating that he wasn't the only person living in the house would be enough for Auror Harrison to justify further investigation.

The basement, ground, and first floors were clear. Sirius mainly kept to his room and the dining room, and Kreacher was always prompt at clearing away the dishes. The real problem would come when they reached Sirius' room. Just like Father had never checked Regulus' room to make sure there was nothing incriminating, Regulus had no idea what Sirius' room looked like.

They made their way to the second floor. Auror Harrison opened the door to the study, and walked to the desk. "The Magic of Life and Death, a Study of the Works of Herpo the Foul," he said, reading the cover of the book.

Regulus gritted his teeth. In all his worrying about Sirius he hadn't even thought of what Auror Harrison would think of that. He glanced at the part of the desk where he had quickly hidden it when Sirius came barging in earlier, his heart pounding. It would be alright though. Even if Auror Harrison found it, he wouldn't figure out what it was, right?

"Tell me, Mr Black, why would you be reading a book like this?"

Regulus had to remind himself to breath, It would be alright, he had lied his way out of worse situations than this. "There… There's a lot of cursed objects that I inherited from my father, I've been researching how to break the curses," he said.

"Why not simply hire a curse-breaker?"

"I prefer to keep things in the family."

Auror Harrison smirked. "Things like the location of Sirius Black?"

"Sirius isn't part of the family," Regulus said, fighting against the stiffness that tried to creep into his voice.

"Yes, so you say," Auror Harrison said. "I actually have a few questions for you about that."

Regulus took a deep breath, and nodded. Auror Harrison would try to trip him up with his questions, Regulus was sure of it. This would be a battle of quick thinking.

"Your parents disowned Sirius because of his willingness to interact with Muggles, Muggleborns, and Half-bloods, correct?"

Regulus thought for a moment. Bella had always said that even when the person questioning you is right, you shouldn't tell them that, or they'll assume they're right about everything. "My parents disowned him because he disrespected the family, our name, and our traditions," he said.

"Interesting that he was never accepted back into the fold after he began supporting the family values," Auror Harrison said.

"I wouldn't expect you to understand," Regulus said. "Serving He-Who-Must-Not-Be-Named does not equate upholding the family values. There is more to the house of Black than that."

Auror Harrison looked almost surprised for a moment, before his expression cleared. "It certainly looks like they're the same thing. Can you honestly tell me there is a single Black, disowned or not, that is not prejudiced against muggle-borns?"

Regulus' eyebrow lifted a little. "Perhaps you should ask your trainee about that. I'm sure they'd be delighted at the implications about their mother."

The silence that followed was almost physical. Regulus could hear his heart pounding in his ears. Actually he could hear everything, not literally of course, but it all seemed louder. Sirius' panting in dog form, the clock ticking on the wall, the muttering of one of Father's books on dark magic, the strange whirring sound he could never find the source of, and the various creaks and bumps that were common in Grimmauld Place.

It was Tonks that finally broke the silence with a cough that was clearly fake. One glance at them confirmed that they were disguising a laugh, and not simply trying to break the silence. "Should we continue with the search?" they said awkwardly as they realized all eyes in the room had turned to them (including the portrait of Antares Black that stubbornly refused to leave the mantle, and the eye that was set in the door to the safe).

Auror Harrison cast Regulus an angry look then turned to face Tonks. "Before we do, I'd like you to do a scan for cursed objects rated XXXX or XXXXX."

Once again Regulus gritted his teeth and made sure his occlumency was well in place. While he didn't technically know what it was rated, but it wouldn't surprise him if it was XXXXX. If it was, he would need a good excuse and a way to convince them not to confiscate it.

Tonks pulled out their wand, and muttered the spell. Only they would be able to see the thread that shot out of their wand leading to any objects. Regulus' heart dropped as she walked towards the desk drawer and pulled it open.

"Finite," they muttered. "Wingardium Leviosa." The locket slowly levitated out of the drawer. "The spell says it's XXXXX. Only thing it found though."

Auror Harrison turned towards Regulus with a smirk. "Mr Black, do you know what this is?"

"I inherited it, along with the rest of the estate. I have been trying to discover what the curse is and how to break it." Regulus' heart felt like it was pounding out of his chest.

Sirius let out a low growl. It took all of Regulus' self control not to shoot him a warning look. Auror Herrison would be watching everything he did. One small mistake and it would be over.

"With it being an unknown curse I have been following the ministry Guidelines for the Protection of Unwitting Children and Guests. When I'm not studying it I keep it locked in the safe. I was studying when you arrived and didn't have time to lock it up so I put it in a closed location, per the guidelines," Regulus continued.

"Well, no need to worry about it anymore. We'll take it to the ministry's Curse Investigation Office for you," Auror Harrison said. "Mx Tonks, please secure the artifact in a curse safe bag, then we'll be on our way."

"I would rather—"

"Keep things in the family?" Auror Harrison cut Regulus off. "I understand. But the ministry can't allow something this dangerous to remain in the wrong hands." He turned to leave.

With a sharp crack, Kreacher appeared next to the desk. Immediately Auror Harrison had his wand drawn and pointed at Kreacher. Regulus stepped closer to them, holding his hand towards Auror Harrison in a gesture meant to give him pause.

"This is my house elf, I sent him on an errand just before you arrived, he's simply returning from the errand."

"And what errand was that?" Auror Harrison asked.

Regulus hesitated a moment, searching for a good excuse. "I sent him to fetch me an old newspaper so I could test the effects of the artifact on paper. Of course that will no longer be necessary now that you've confiscated it."

After a moment of consideration Auror Harrison lowered his wand. "Very well. We'll be going now. Mx Tonks." He turned and left the study.

Tonks, however, hesitated a moment longer, looking between Regulus and the paper in Kreacher's hands with thinly veiled suspicion. Finally after what seemed like ages they spoke. "Have a good afternoon," They said.

Sirius turned human the second the door was shut behind Tonks and Auror Harrison. "XXXXX do you have any idea how dangerous that is?" he said.

Regulus let out a string of curse words, both wizard and muggle, and completely ignored him. Instead he turned back up the stairs towards the study, Sirius following close behind. Regulus had never been one to curse, no matter what the situation was.

They entered the study, where Kreacher was still standing looking ridiculously distressed, like he usually did. "Kreacher is sorry if he caused trouble for master Regulus. He will punish himself most thoroughly," he said.

"You don't need to punish yourself, you did nothing wrong." The tension in Regulus' voice was clear.

"Are you just going to ignore me again? I was right, wasn't I? I can tell when you're lying, you weren't trying to break whatever curse is on it, you were experimenting with Dark Magic."

"Sirius, please let me handle this. You don't understand."

"Clearly neither do you!"

"No, I don't. But I'm the only one I trust who might," Regulus snapped. He took the paper from Kreature. "Thank you Kreacher, that will be all for now."

"Oh go on, change the subject!"

"Do you want to find Pettigrew or not?" Regulus snapped. "The boy that has him is one of Arthur Weasley's children. Not that I know how that will help us, we can't exactly show up at their house and demand they give us their rat."

"So we'll sneak in."

"Besides, who knows when they'll be back in the country."

"So we'll wait for them!"

Regulus huffed. "Do what you want, I have more important things to take care of."

"More—" Sirius let out a laugh. Regulus must be mad! This was Harry's life on the line! If they didn't catch Peter before the beginning of the school year, he could kill Harry at any time he pleased! "More important than Harry's life?" Sirius hoped the anger in his voice was enough to knock Regulus from whatever high horse he was sitting on.

"Quite frankly, yes," Regulus said sharply.

"HOW COULD YOU SAY THAT?" Sirius shouted. "HARRY IS ALL I HAVE LEFT OF JAMES AND LILY, DON'T YOU GET THAT? IT'S MY FAULT THEY'RE DEAD, I CAN'T LET HIM KILL HARRY TOO!"

Regulus turned around. "And what value is Harry's life if the dark lord returns?"

"You fucking Death Eaters and your stupid loyalty!" Sirius shouted. "You Know Who is dead! I saw his body. He's gone forever and he's never coming back. You lost."

"No he's not, you don't understand! He can't die!" An edge of panic inched it's way into Regulus' voice.

"And here I was, thinking you didn't still support him," Sirius said. He tried to keep his face a mask of anger, or disgust, or anything to keep Regulus from seeing how much it hurt. He really thought Regulus had changed. That maybe, even just a little bit, he had escaped from their parents' brainwashing.

"Would you just listen to me?" Regulus said. "For once in your life just listen, please!" Regulus' voice cracked. He leaned against the desk, taking several deep breaths. "Almost two years before the Dark Lord fell, just after father died, the Dark Lord pulled me aside after a meeting. He told me he needed a house elf he could use, he didn't tell me why, or what he needed him for, but I agreed to let him use Kreacher. I told Kreacher to do whatever the Dark Lord said, then to come home. The Dark Lord didn't intend for him to come home. When Kreacher came back he was in bad shape. He said the Dark Lord took him to a cave, forced him to drink a potion, then placed an object in the bason, refilled the potion, and left."

Sirius couldn't help the sick feeling welling up in his gut as Regulus paused to take several deep breaths. He hadn't felt like this since the first war, not really.

"I'd heard whispers, conversation before or after meetings, rumors mostly, that he'd found a way to ensure he couldn't be killed. Near the same time I heard Bella and Rebastian boasting that he trusted them with a precious artifact. I didn't put together that they might be related until after Kreacher came back from the cave. After that I kept my eyes and ears open. I paid more attention to the rumors and whispers and I studied. I finally figured out what it was. He had made a horcrux, at least two, and unless they're destroyed he can't die. Not really. His body may be destroyed, but he could be brought back. That's what they took, that's why I have to get it back."

Sirius' head was spinning. He had heard father talking about horcruxes when he was younger. He had called them effective, but too desperate of an action for any reasonable pure-blood to take. If You Know Who had a horcrux, if he wasn't really dead, then James and Lily had died for nothing… and not just them. James, Lily, Marlene, Dorcas, all of them.

"If we destroy it, he'll be dead?" Sirius asked.

"Them. I think he made more than one. But yes, if we destroy them there will be nothing tying him to this world. He'll be dead."

Sirius muttered a curse under his breath. He had to save Harry, but at the same time.

"I'll help you stop Peter," Regulus said. "But you have to understand, my priority is destroying the Horcruxes."

"My priority is keeping Harry safe," Sirius said. "But you're right, until You Know Who is gone for good, Harry won't really be safe."