Hogwarts

"Stop being so childish," Sirius muttered, rolling his eyes.

"I wanted to see if a House Elf could circumvent..." Regulus started saying, his mouth forming a pout.

"Focus," Sirius said, glancing around Albus Dumbledore's office. He let out a deep sigh. "Didn't expect to be back here so soon."

"It's nice to have you here and not be because you're getting into trouble," Dumbledore said, grinning at Sirius. "Your message said you've already located two of the three potential Horcruxes."

"Yes," Sirius said. "My brother's a weird little..." He paused, then turned his head. "Regulus! Don't touch that!"

Regulus turned, frowning, his fingers reaching out towards one of the delicate devices in Dumbledore's office. He turned, still pouting.

"He's fine," Dumbledore said. "I've always admired his curiosity."

"Fawkes is still here," Regulus said, suddenly distracted by something else, this time the phoenix in Dumbledore's office. He walked over, reaching a finger up, smiling at the creature who bent its head down so Regulus could scratch its chin. "It's nice to see you again."

Sirius frowned. "Focus, Regulus."

Regulus' eyes blinked, and then he opened the bag they'd placed the Horcrux in. "We need a Basilisk tooth. Do you know how we can enter?"

"Well, through the Boy-Who-Lived," Dumbledore said. "At least I would presume." He stood. "However, there may be a much easier solution at hand."

"Really?" Regulus asked.

"You're way too chipper," Sirius said. And then he paused, taking in a deep breath. "You've not commented on his arm?"

"I'd already had the feeling your brother's been through a lot, Mr. Black," Dumbledore said, standing up and walking over to a counter.. "But it's nice to know what he went through didn't break him, changing who he is at the core."

Sirius frowned, then let out a sigh. "Must learn not to ask things of this man. He remains as elusive and as eccentric as..." Sirius paused, his eyes blinking. "Regulus."

"Yes?"

"Nothing," Sirius said.

"Anyways," Dumbledore opened the cabinet. "You'll be wanting this."

"This?" Regulus turned his attention to their former headmaster, and then his eyes widened, his mouth forming a circle. "The sword of Gryffindor."

Sirius watched his brother hurry over, his head tilting and his body leaning as he examined the magical item in Dumbledore's hands. "The sword?"

"It should have absorbed the Basalik poison."

"Hear that?" Regulus said. "You can wield it."

"Me?" Sirius let out a huff.

"You're the one who was sorted into Gryffindor."

Dumbledore reached out for Regulus' hand, moving it to his hilt. "I think you underestimate yourself, young man."

Dumbledore let go of the sword, and Regulus nearly dropped it, only for his right hand to reach out to grab it. "I think Sirius should carry it." He turned to look at Sirius. "It's also good that there aren't any students around, or at least very few. Let's go."

"Hold on," Sirius said, letting out a sigh. He let out a yelp as Regulus shoved a sword towards him. "Be careful with that! It's a sharp object, Regulus." And then—

Regulus headed to the exit of the headmaster's office.

"Hey! Get back here!" Sirius let out a sigh.

"Be patient with him, Mr. Black. His mind has always been, well, unique. It seems like he also feels a lot more freedom to be himself."

Sirius frowned. "Meaning?"

"I'm sure that Walburga Black wasn't fond of the questions arising from an inquisitive mind," Dumbledore said. "But you should keep up with him."

Sirius sighed, hurrying after Regulus, almost missing his brother turning down a particular hallway. "Where? Where are we going, Regulus?"

"To see the ghost of Ravenclaw," Regulus said.

Sirius' eyes blinked. "That?" He nodded his head. "For some reason that actually makes sense."

"Not sure if she'll help us, though," Regulus said. "She can be quite moody."

"That..." Sirius said, frowning. "Why would you know something like that?"

"Ghosts are a lot easier to converse with than living people."

Sirius' jaw dropped. "In other words, you made friends with the ghosts here?"

Regulus paused, looking at his brother, tilting his head. "You know, I think you're right, now that I think of it. You're probably right."

Sirius shook his head, following after his brother for what felt like forever, as finding a ghost at Hogwarts turned out much harder than he expected. But then Regulus spotted her, hurrying over to her. "Ms. Helena?"

Sirius watched the ghost stiffen, not thinking that even possible. She looked at them, her nose turning up, but then her head tilted, inquisitive. "Wait. I believe I know you." She then frowned at Sirius. "And I certainly know you, Sirius Black."

"Pleasure to meet you, lady," Sirius said, putting on the charm, earning him glares from both Regulus and Helena, as Regulus called the Grey Lady.

"Don't," Regulus said. "You're far from her type."

"Excuse me?"

"Now that I think of it," Helena said. "But I would have thought I'd seen you here as a ghost, not in flesh, Regulus Black."

"I'm alive. And well."

"Doubtful." She looked at his arm. "You came back after all this time, after not bothering to graduate—"

"Hey!" Sirius said.

"She's not wrong," Regulus said.

"You've a reason?"

"I'm seeking to destroy parts of his soul," Regulus said. "To prevent him from coming back."

"His soul?" She grimaced.

"I think you know where a piece is."

"That room you like to hide in, when things got rough," Helena said. "That's the place to look. That's where he hid it, in a place of hiding things. But I trust you, but you really should have been sorted into my house, Regulus Black. You would have been much safer, and not as alone as you thought."

"What is she talking about?" Sirius said, following after his brother. "And what did she mean about being sorted into her house?"

"It's the Come and Go Room," Regulus said, hurrying up to the seventh floor where he kept going round and round. "And I was given a choice. Between Slytherin and Ravenclaw, but as she said, I was scared to be alone. Cissy was in Slytherin so that I wouldn't be alone."

"That..." Sirius frowned. "And I thought his choice was simply about being loyal to family. Well, in a way. Family is perhaps important to him, but not how I thought."

And then—

Sirius blinked. "Wait? That room?"

"The Come and Go Room," Regulus said, opening the door. "She noted the need for hiding something, so..." He stepped in, Sirius following him, his eyes blinking. "Oh."

"Yeah, oh is right," Sirius sighed. "It's going to take forever to find the damn thing, isn't it."

Regulus sighed. "Well, we should get going."

"Says the person not carrying a sword," Sirius muttered. "Can't we just summon it?"

"Nope," Regulus said.

Sirius sighed.

"Let's start by looking at what's in sight of the eye, including things we can open."

"I'm wary of opening anything in here, Regulus," Sirius said, and then, "But obviously you're not! You'd better practice proper precaution."

"I'll be fine."

"How about we start by not opening things up and just looking for things within our eyesight?"

"Fine."

And then—

At the end of the day, Sirius felt utterly lost, unsure of which direction they'd already gone, yet Regulus easily said, "No. We've already been down that way, and it was a dead end."

"How do you do it?"

"What?"

"Keep track of the details?"

"Muggles call eidetic memory," Regulus said. "Though it's honestly a pain in the neck." He stopped, then turned, frowning, his hands forming fists. "Hey, Sirius?"

"What?"

"My ability to recall things?" Regulus said. "That's what he wanted me for."

"Why are you telling me this?"

"Because," Regulus said. "The subject came up, in a way, and I wanted it off my chest. But I'm aware, all too well now, that what I thought was up was actually down."

"You're not making any..." Sirius paused, then pointed. "A diadem is a kind of crown, right?"

"Yes," Regulus said. He frowned. "And that, I think, is it." He picked it up, putting it on the ground. "So, destroy it."

"I think you should."

"What? No?" Regulus said. "I'm not." His right hand was on his left arm. "It's a two-handed job, and even with this device."

"What about a three-handed job?" Sirius said. "Put both your hands on the hilt, and I'll put mine on top of yours."

"That..." Regulus frowned.

"Grandfather said you must finish what you started, so let's."

Regulus nodded his head, and they proceeded to push the sword into the diadem, watching it shatter. They repeated with the cup and moved on to the locket, when—

The locket opened, a pair of creepy eyes looking at them, and an apparition of their mother appeared. Sirius almost barked out something, yelled at her as he usually did, only—

Walburga Black spoke in French, her attention upon Regulus, cursing him out as he grimaced, his teeth gritting together. Sirius watched. "What did you go through with her, that she made you like this?" He took a deep breath. "Ignore her. What does she say? It doesn't matter? Kill the locket."

And then Regulus pushed down, Sirius lending him his strength, and the apparition ended. His brother pulled away, shaking, and started to babble. Sirius let the sword drop, quickly moving over to his brother and pulling him into a hug.

"It's okay. It's okay. All of this is over. You've done what you've set out to do, Regulus."