Title: By Virtue (Of Being Who You Are)
Pairing: Harry/Regulus
Content Notes: AU fifth year, weird magic, angst, mentions of injury
Rating: PG-13

If it were any other year, Harry probably wouldn't have done it. He would have handed the problem off to Professor Dumbledore, or Flooed Sirius and asked him what to do. Or he would have been walking with Ron and Hermione, and they would have helped him understand what to do, since he probably wouldn't have known.

But Dumbledore hadn't talked to him all year, and Umbridge was watching the Floos, and Harry was wandering around the dungeons, alone, under his Invisibility Cloak, and thinking murderous thoughts about Umbridge as his hand ached.

The wall opened, and a boy stumbled out of it and dropped senseless at Harry's feet.

Harry stopped and stared at him. He wasn't anyone Harry knew, although there was something a little familiar about his face. He had tangled dark hair, and the way he was sprawled, Harry couldn't see him well.

He glanced back at the wall, wondering if it was like the Room of Requirement, but it had already closed.

Harry stared once more at the boy. Then he cast a Feather-Light Charm on him and dragged him under the Invisibility Cloak to take to the actual Room of Requirement.

For the first time all year, he was distracted from the pain in his hand and thoughts of Voldemort.

The boy wore Hogwarts black robes, but he was very definitely not someone Harry had seen before. He woke up not long after they were in the comfortable, small version of the Gryffindor common room that Harry had asked the Room for. He clenched the cushions and bolted up, staring around. Then he stared at Harry.

"Where am I? Who are you?"

Harry put down his hot chocolate, and blinked. That, he hadn't expected. Surely the boy would know him even if Harry didn't recognize him? "I'm Harry. You know, Harry Potter?"

"Are you related to James Potter?"

"His son," Harry said, slowly.

The boy recoiled from him, and then bowed his head. Harry stared at his face in the shadowed firelight, and the nagging familiarity returned again. The boy did look like someone, he must be related to someone Harry knew, but who?

"I did it, I did it," the boy was murmuring nonsensically.

"What are you talking about?"

The boy looked up and licked his lips. He had striking features and grey eyes—and then Harry caught his breath with a gasp, because he did know where he had seen that face before. The boy nodded as if hearing his thoughts.

"My name is Regulus Black," he said. "And, and I know this is going to sound strange, but—but I did it. I'm from 1976. Hear me out before you decide I'm mad, all right?"

Harry thought of the papers calling him mad all year, and experienced a strong surge of fellow feeling for Regulus.

"I'm listening," he said.

The story Regulus told was incredible. Not exactly time travel, and not something like being trapped in the walls of Hogwarts for years, either. Apparently he had existed, and a version of him, Sirius's younger brother, had gone on and died, the way Sirius had shown Harry on the Black family tapestry over the summer. But Regulus had suspected that something bad was coming for him, and had worked magic that involved runes and blood and potions and Transfiguration and even the position of stars and the presence of snake venom to—break off a version of himself, somehow. Like a splinter. That version had frozen in time, and been stored in a tunnel that Regulus himself had never walked down, only to move slowly, parallel to the time in the real world, until he reached a certain point.

"What point?" Harry demanded. He was fascinated. His hot chocolate had long since got cold beside him.

"When the magic sensed that someone was passing by who was sympathetic, and would help me," Regulus said. He had hot chocolate of his own, and he seemed to huddle around it, as if wherever he had been was colder than the inside of the moon. "And someone who—" He broke off and stared at Harry.

"What?"

"Someone who had the power to defeat the Dark Lord," Regulus said quietly. "That was what really pushed him to do it—the other version of me, I mean. He knew that he didn't have any choice about becoming a Death Eater, and part of him was excited about it, but part of him wasn't." He rubbed his hand over his chest. "I'm the part that wasn't. So he sent me into a future where he hoped I'd have peace."

Harry snorted. "Better to have you wait until Voldemort was defeated, then."

"But you have the power." Regulus sat up and spoke with more confidence. "You didn't deny it. And you said his name."

Harry eyed him, savoring the last moments of someone not knowing who he was, and then nodded sharply. "Yeah. He tried to kill me when I was a baby, and the spell backlashed and killed him. Don't exactly know why.'

"What spell was it?"

"The Killing Curse."

Regulus's eyes widened, and Harry grimaced a little at the change in them. He hated it when people hero-worshiped him.

But there was a difference. Regulus proved it when he turned to Harry and said simply, "Tell me how I can help."

It probably wasn't the right thing to do, but Regulus asked Harry to keep him a secret from the populace of Hogwarts, and Harry agreed. It was sort of—nice to have a secret to himself. Just one. And Regulus couldn't possibly make the situation worse than it was already. He hadn't caused Dumbledore to turn away from Harry, and he hadn't brought Umbridge here or started torturing Harry with a quill.

Regulus was able to do something about the quill's after-effects, though.

"My mother used to use one on me," he murmured as he wrapped bandages soaked in Murtlap Essence around Harry's scar. "And I found out that if you use a lot of it, and then drink some of it diluted with water, it'll reduce the pain to a manageable level."

Harry nodded, watching as Regulus's fingers worked. They were once again in the comfortable firelight of the Room of Requirement. Regulus stayed there most of the time, except when Harry and his friends wanted to practice their spells with the DA. Harry would warn Regulus ahead of time, and he went and hid elsewhere until they were finished.

"That's not the only scar you have, I notice."

Regulus was looking at the basilisk scar on Harry's arm. Harry covered it with a palm, self-consciously. "Yeah."

"What's that from?"

Again and again Harry forgot that Regulus didn't know the things that were common knowledge among his friends. He coughed and muttered, "I fought a basilisk in my second year when a student was possessed and letting it out of the Chamber of Secrets."

"What?"

And Regulus listened, enthralled, as Harry described the story. Harry thought he was a very good audience. He seemed suitably impressed and wouldn't scold Harry for getting into danger like an adult (or Hermione), but also didn't jump and flinch and scream and act like the story was too scary to listen to.

When Harry told him about the diary, he got a very peculiar look on his face.

"What?"

"I need to research something. Can you request that the Room give me the books I need?"

"You can request that yourself," Harry said, and Regulus gave him a long, careful glance before he stood and asked, in a voice that said he expected to be denied. But the room shivered and gave him a long pile of books that tumbled from the shelves, although they hadn't been there a moment before, and piled up on the floor at his feet.

"What's Horcruxes?" Harry asked.

"I'll tell you about it in a while. Now, please let me research, Harry."

Harry nodded, and left him to it. He didn't mind, because when Regulus said he was going to tell Harry something later, he always kept his word. Unlike people like Dumbledore, who still hadn't told Harry the reason Voldemort had wanted to kill him.

When Regulus had explained what Horcruxes were and why he thought the diary had been one, Harry just sat and stared at the fire in the Room of Requirement for a long moment. Then he glanced at Regulus.

"Do you think that was the only one he had?"

Regulus shut his eyes. "I wish you hadn't asked that, Harry."

"You don't think it was."

"No," Regulus whispered. "My cousin, Bellatrix Lestrange, she—she bragged a few years ago, I mean a few years ago in my time, about being given something powerful and important to hold for the Dark Lord. I don't know what else it could have been."

Harry nodded slowly. "Then I need to start thinking about how to destroy them and take him down," he muttered. "At least I know that basilisk venom destroys them."

"We need to start thinking."

Harry turned and stared at Regulus. He could feel his eyes widening. Regulus looked frightened but determined, reminding Harry of Neville in their first year when he'd tried to stop Ron, Hermione, and Harry from leaving Gryffindor Tower.

"Regulus. I can't let you do that. It's not your responsibility."

"No?" Regulus lifted his chin, and yes, he looked honestly terrified, but his hands were also clenching into fists. "My other self was afraid enough of the Dark Lord to try and send me through time and space until I could find someone who would destroy him. And I found him. But I also think that he needs my help."

Harry just opened his mouth and then had nothing to say, because that was the first time anyone other than one of his friends had offered to stand with him.

He ended up smiling at Regulus, and Regulus flushed as he stared back. Harry reached out and squeezed his arm, nodding, and hoping that was enough to convey everything he was feeling, which he would have trouble putting in words.

It seemed to be, because Regulus smiled, cleared his throat, and started talking about how they could recognize a Horcrux, since not every one might possess people like the diary. Harry found his eyes lingering on the way that Regulus's hands moved, and how his throat worked.

He had a highly confusing dream that night, and woke up with a flush of his own. But he was smiling the next day when he went to meet Regulus, and from the glances Regulus darted at Harry, he wasn't alone.

Even knowing that Voldemort probably had multiple Horcruxes and there was no saying how many there were or how hard they would be to find and destroy, Harry found himself smiling a lot more than usual.

If he had to take the first steps on a long road, it was good to have someone at his side.