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Doppelgänger

Summary:

/ˈdɑpəlˌɡɛŋəɹ/ · noun. a person who is almost identical to another.

almost being the operative word.

OR

Walburga has had it with the Heir Apparent, and forces Regulus to drink Polyjuice Potion to pretend to be Sirius at Hogwarts. How hard could it be to impersonate Sirius Black, the most obnoxious brother known to man?

Chapter 1: A Clever Plan

Notes:

(See the end of the chapter for notes.)

Chapter Text

April 1975

 

Friday, April 17th, Sirius Black received a letter. The family owl unceremoniously dumped it onto his breakfast plate, ruining his carefully arranged spread of pastries and eggs, and simultaneously, ruining his morning. Sirius picked the greasy letter off his breakfast plate, handling it as if it were a particularly ripe banana peel he’d just plucked from the garbage.

 

At the exact same moment, Regulus received an identical letter carefully placed on an empty spot on the table. Both brothers were too preoccupied to meet each others’ eye across the Great Hall.

 

Sirius peered down at the family crest stamped onto the envelope, Toujours pur engraved in dark green wax, sealing the letter closed. Sirius could tell from the address that Walburga had sent it.

 

James eyed him across the table. “That from you-know-who?” 

 

Sirius blinked. “Yeah, looks like it.”

 

James shook his head, and without missing a beat, asked, “once you’ve opened it, can I burn it?”

 

Sirius laughed, but it felt slightly forced. His family hardly contacted him these days; they most certainly didn’t send him letters to exchange small talk. Whatever was in this letter, it had to be important, which meant it was something Sirius probably didn’t want to know. He debated not opening it at all, stuffing it in his bag to deal with later, but he knew he would agonize over not knowing just as much as he’d likely agonized over knowing.

 

He sighed and slid his butterknife under the seal, breaking open the letter and freeing the words on the page. His eyes skimmed Walburga’s scrawling cursive, and his face fell rapidly.

 

“What is it?” James asked, mid-buttering his third piece of toast.

 

Sirius swallowed hard, and found the words wouldn’t come. Walburga always had the uncanny ability to silence him even from kilometers away.

 

“Sirius?” Remus asked again, and Sirius shook himself from his thoughts.

 

“I’ve got to go home this weekend,” he said dully, forcing his tone to remain even, “Wally’s arranged it all with Dumbles, I guess. We leave tonight.”

 

“That’s shit, Pads,” Peter said immediately.

 

“Why would Dumbledore approve that?” Remus asked, anger evident in his tone.

 

“More importantly,” James cut in, “what does she want that you have to go home for? What can’t wait?”

 

Sirius found himself scanning the Slytherin table for Regulus, and their eyes locked. Their relationship had taken a turn for the worse this year, as Sirius did everything in his power to rebel against the House of Black as Regulus seemed to fall further into it. But he saw his own trepidation matched on Regulus’s face, and this brought him some comfort, though minimal.

 

“Who knows,” Sirius laughed, trying to ease the tension, “she’s proper insane if you ask me.”

 

He made a valiant effort to return to his breakfast, but his carefully selected pastries now felt tainted. Sirius reached for a biscuit instead, gnawing on a corner. 

 

“You said we --” Remus started, but Sirius threw him a scathing look and Remus quickly, and wisely, let the sentence hang. His friends knew better than to mention his brother, especially so early in the morning and without any alcohol in his system to soften the blow.

 

He felt Regulus’s eyes on him for the rest of breakfast, but he couldn’t bring himself to meet his brother’s eyes again.

 

Sirius did his best to act normal for the rest of the day, but it was like the words from the letter had bled off the parchment and painted themselves across his skin. Every step he took, every muscle he flexed, seemed to remind him of what was waiting for him that evening. In a few short hours he’d be off to Grimmauld Place, with no one but Regulus to witness what transpired. No one to save him.

 

You have disappointed us for the last time, the closing line of the letter read, and we will tolerate your insolence no longer. You will learn, Sirius, or you may die trying. 

 

Sirius swallowed hard. He wasn’t even sure what he’d done this time, to be honest, but that hardly seemed to matter to Walburga these days. Any small infraction was cause to punish him, cause to bloody him beyond recognition to shape him into a better, more noble heir.

 

Once they’d returned to their dorm for the evening, he packed for Grimmauld in relative silence, and his friends watched him grimly.

 

“Just two days, Pads,” James said reassuringly.

 

A lot could happen in two days.

 

“Maybe just…keep your head down?” Peter squeaked, and Sirius found he didn’t even have the energy to spare to snap at him for such a stupid remark.

 

“We’ll be here when you get back, Pads. Whatever you need, yeah?” Remus said softly, twisting his sweater in his hands, a nervous tell.

 

Sirius looked up from his trunk then, taking in his friends’ anxious faces.

 

“Godric, you lot need to worry less,” he joked, “I’m not off to a funeral. It’ll be fine; I’ll be fine.”

 

He wasn’t sure if he was trying to reassure them or himself.

 

He levitated his trunk beside him down to Dumbledore’s office, turning down his friends’ offer to accompany him. The halls were deserted, everyone off having fun with their Friday night, and the thought did nothing to lessen Sirius’s foul mood.

 

“Fizzing whizzbees,” he hissed angrily at Dumbledore’s guardian gargoyle, and it spun to reveal the stone staircase.

 

Sirius stomped up the steps, trunk floating behind him, and knocked hard on Dumbledore’s office door.

 

“Enter, my boy,” Dumbledore called, and Sirius opened the door to Dumbledore’s study to see Regulus already standing there.

 

“Ah, right on time!” Dumbledore sang, eyeing Sirius’s trunk. “You two ready to go?”

 

“Yup,” Sirius said, popping the ‘p’. 

 

“Yes, sir,” Regulus replied, always one to follow proper decorum.

 

“Excellent, excellent,” Dumbledore said, “I’ve created this portkey to bring you back to Grimmauld Place.”

 

He held out a gobstone to them, and both brothers regarded it dubiously. 

 

“Now just hold it between you like this--” and Dumbledore pushed the gobstone into Sirius’s hand, then dragged Regulus’s hand on top of it. They both kept their free hand on their trunk.

 

The three of them stood there in silence as the seconds ticked by, and with them, Sirius grew to doubt his own sanity as well as Dumbledore’s.

 

“Are you sure this--” and the rest of Sirius’s question died on his lips as he felt the sensation of a hook just behind his navel yank him away from Dumbledore’s office.

 

In an instant, the two Blacks were on the landing of Grimmauld Place, breathing hard.

 

“What…” Sirius panted, “the fuck…was that…”

 

“I think-- I think I’m going to be sick,” Regulus croaked, and he leaned toward the bushes framing the sidewalk, but nothing happened.

 

“Godric, I will never agree to do that again,” Sirius wheezed.

 

Regulus nodded in agreement, until both brothers realized they were having a somewhat friendly conversation, and silence fell between them once more.

 

Sirius waited until Regulus straightened before asking, “shall we?”

 

Regulus gave him a curt nod, and the two entered Grimmauld Place.

 

Walburga was on them in an instant, as if she’d been waiting in the foyer for their arrival, which didn’t bode well for Sirius.

 

“Regulus, my darling boy,” she cooed, “oh, how I’ve missed you. Go unpack, I’ll be up to see you shortly.”

 

“Yes, maman,” Regulus said shortly, dragging his suitcase up the stairs without sparing Sirius a parting glance.

 

“Sirius,” she said coolly, but her eyes were sparkling, “join us in the study, won’t you? We have much to discuss.”

 

Despite every instinct in his body telling him not to follow her, Sirius knew he didn’t really have a choice. He left his belongings behind in the entryway and followed his mother to the study.

 

The study was Sirius’s least favorite room here at Grimmauld, his least favorite place. The study was where Orion sat behind a tall mahogany desk, sipping large amounts of amber liquid in a short glass, regarding him like a particularly bothersome bug. Squinting at him and mocking him until he got bored of the insults, and turned things over to Walburga. Walburga had always been better at driving a point home; using her wand and her words and her nails to draw blood of all kinds.

 

Tonight began no differently. Sirius sat in the same seat, endured Orion’s classic you-are-a-disappointment-to-the-House-of-Black speech, and spoke only when spoken to. He couldn’t understand what about this necessitated him being brought home from Hogwarts. Finally, Orion’s speech changed, and the new words caught Sirius’s attention against his will.

 

“You know,” Orion mused, “it’s rather interesting, what we heard recently. Venture a guess, Sirius, as to what it was?”

 

Sirius knew a trap when he heard one. “I don’t know, sir,” he said through clenched teeth, trying desperately not to let his frustration get the better of him.

 

“Well, you see, our family is so well-connected. It’s a shame, really, you’re so hellbent on defying us, Sirius. We could work so well together, if you’d give us the chance.”

 

Sirius stared back unblinking, and his father continued.

 

“One of our esteemed connections has raised some rather egregious concerns about your activities at school.”

 

Sirius nodded, not sure what he was agreeing to but not willing to open his mouth to speak, either.

 

“It really is dreadful, Sirius, the things she said.” Orion paused here to take a long sip of his drink, leaving Sirius hanging on the silence. 

 

“But I’m sure, I’m sure, we’ll get to the bottom of this horrid business.”

 

And Sirius knew that Orion was baiting him, knew that he wanted Sirius to ask what this dreadful business was, and Sirius couldn’t help himself; as much as he hated playing into Orion’s hand, he needed to know.

 

“What’d she say?” he asked, hating the way the words felt on his tongue almost as much as he hated hearing them fall from his mouth.

 

Orion’s eyes lit up. “I’m so glad you ask, Sirius. You see, and I can’t believe I’m forced to push these words past my own two lips, she said that you’ve been fraternizing with a halfblood. And not only is he a halfblood, he’s a-- my, my, my, Sirius. He’s a werewolf, too.”

 

Every single feeling in Sirius’s body was replaced with leaden terror.

 

Silence sat in the study between Sirius and his parents, the occasional clink of ice in Orion’s glass the only sound to disrupt it.

 

“Well?” Walburga shrieked eventually after the silence had dragged on, “is it true? Have you dirtied yourself with a beast?”

 

And for one single, unchangeable moment, Sirius forgot himself.

 

“He is not a beast he is--” 

 

Orion hurled his glass at Sirius, and the impact of the glass on his throat left him gasping for air, the alcohol soaking his shirt like an afterthought. 

 

“Oh, Sirius,” Orion chuckled darkly, but there was nothing funny about any of this, “I thought you’d disappointed us before but this? This is low, even for you.”

 

Sirius breathed hard, feeling a bit like the glass had crushed his very lungs. He almost wished it had.

 

“We can help with that, of course,” Walburga hissed gleefully, “we’ll make an heir out of you yet. And I know just how to start.”

 

“Crucio!” Walburga shrieked, and Sirius had exactly one second to fear for his life before it all went black.

 

- - -

 

Regulus sat on his bed and, as he did best, he worried. Sirius had clearly done something idiotic and foolish enough to warrant this surprise trip home, but this was hardly surprising. His brother had reached new heights of rebellion this past year; it would’ve been more surprising if Sirius hadn’t done something to royally piss his parents off.

 

It was still concerning, though. They’d never felt the need to bring them both home during the school year before, and Regulus missed the relative safety of Hogwarts.

 

He tried to distract himself by reading the assigned chapters for Defense Against the Dark Arts, but his traitorous brain kept drifting away from the book and down the stairs to Orion’s study, where Regulus was sure the rest of his family had gathered. As the hours ticked by, Regulus's restlessness grew, and he eventually gave up the pretense of reading altogether to lie on his bed and stare up at his ceiling. He couldn’t go to bed because his mother had specifically said she’d be up, which meant Regulus was forced to wait.

 

Close to midnight, she knocked on his door and entered moments later. She crossed the space and came to sit next to him on the bed, and Regulus’s alarm grew.

 

“Regulus,” she said sweetly, “how have you been?”

 

“Well, maman, thank you.”

 

Walburga looked at him for a long moment, and Regulus got the distinct impression she was sizing him up.

 

“Your father and I need a favor,” she said carefully, “you always were our better son, always better fit to be the heir.”

 

Regulus’s blood ran cold, but he wouldn’t let his face show it. Walburga asking for a favor? Admitting to needing help? Something terrible had happened downstairs.

 

“Of course, however I can help,” Regulus said, inclining his head, but they were none of the words he wanted to say.

 

“Sirius finds himself…indisposed, for the time being,” Walburga said shortly, and Regulus blinked hard to keep any emotion off his face.

 

She let that hang between them for a moment, testing him, and continued when Regulus kept his face carefully neutral. 

 

“I’m afraid of how it might look, of course, at that wretched school. People talk far too often about things they really shouldn’t.”

 

Regulus nodded slowly, but he had no idea where she was headed with this.

 

“But if you were to go and be the heir, Regulus, well, that would solve all our problems, wouldn’t it?”

 

Regulus stared, and forced himself to speak. “How so?”

 

“Simple. Really, Regulus, do try to keep up,” and she threw him a withering look that made Regulus feel one foot tall, “You go to Hogwarts, as Sirius, and we tell the headmaster you’ve taken ill. You get to play the part of heir, we get some more time to straighten Sirius out, and no  one will even have time to miss him.”

 

Regulus swallowed hard. “What do you mean I go as Sirius?”

 

Walburga grinned, and it looked predatory. “Well, that’s my clever addition to the plan. You use Polyjuice Potion, and no one will be able to tell.”

 

“But Sirius…” and Regulus trailed off, afraid to ask the question he really wanted to ask.

 

“Don’t concern yourself with him,” Walburga hissed, and Regulus flinched in the face of her sudden anger, “maybe you’re not reading me clearly here, Regulus. We are not asking this of you, we are telling you that you will do this to carry out your obligation to this family.”

 

Regulus nodded, desperate to keep Walburga’s anger at bay, “yes, maman, I understand.”

 

Walburga grinned, calm once more. “It’s probably best if you give your brother some additional time to recover, anyways. I’d hate to push him before he was ready, lest something terrible happen.”

 

And Regulus nodded, seeing the threat for what it was. He’d return to Hogwarts, drink the Polyjuice Potion, and pretend to be Sirius. How hard could it be?

 

Notes:

hi besties surprise i decided to drown myself in 2 simultaneous WIPs! this one will be updated on Tuesdays, with the next update being next week :)

this was inspired by a post on tiktok by @almostmarls & i've reposted it on my tiktok account if you'd like to see it! thanks for the idea!

now, let the shenanigans ensue!