Chapter 1
Regulus had always had the fascinating, and often quite useful ability to stay calm when other people didn't.
It was part of his nature: you have a problem, you think about it, you solve it, you don't have a problem anymore. Quietly. Quickly. Panic, did not help. Might even get you a beating or two if you grew up under Walburga's thumb.
So when his waste-of-space, bloodtraitor of a brother decided to set off fireworks in an enclosed classroom, Regulus didn't flinch.
While havoc broke out around him as students screeched and scrambled to cover their ears, Regulus focused on tapping his quill in a slow rhythm, his eyes fixated on Sirius and Potter. Both were grinning from ear to ear, taking in the chaos.
A shrill whistle rang and while it felt like it split Regulus's head at first, it was followed by such blissful quiet he was almost grateful.
"Potter, Black, care to explain yourselves?" asked Professor McGonagall. Thank fucking Salazar.
Regulus schooled his expression, not letting his glee shine through as Sirius and James stood frozen in front of their head of house for a second. If he hadn't known any better he would've said they looked bashful. And then they ruined it by opening their mouths.
"We learned a new containment charm today," Potter said, grinning, while Sirius nodded along.
"And we just had to try it out. I mean ... What would have happened if we ever needed it but it didn't work?"
"Or," Potter cut back in, "if it was too strong ... Never to be escaped again-"
"Cast by two brilliant young wizards, noble and handsome-"
"That, is quite enough Mr. Black."
It wasn't just that he wanted his brother punished, it was the hurt that Sirius put him through time and time again. The way he showed Regulus time and time again how indifferent he was. How much he didn't care.
Sirius used to be the one who did. The only person Regulus trusted, the only one he knew cared more about Regulus than his own benefit.
Most people just didn't know. They didn't know why Regulus couldn't change in front of others or how his brain hurt if the world became too loud. But Sirius knew. He knew it all, he just didn't care. Anymore.
And today it was so evident: Sirius and James had used a clever piece of magic; charming the fireworks to follow them into the classroom as they pretended to ask Professor Binns about Gilly-Weed.
Just before the fireworks went off, Potter had thrown a containing charm at them which meant the tiny explosions had stayed in a large bubble, not to hurt anyone. But all it meant to Regulus was that Sirius had had all the chance in the world to throw a silencing charm at them. Or a muffling charm over him.
But he hadn't. Because he didn't care.
"Detentions, the both of you."
They both nodded and at least Potter had the decency to look halfway bothered by this.
"And now of course," Professor McGonagall added, "you are going to clean up the mess you've made- by hand," she said, snatching the wands they'd drawn and ignoring their weak protests.
"Right," Binns clapped his hands, "now that this is sorted, I ask my students to return to their seats and ehem- where were we ... Yes that's right, No Mr. Potter we do not have any cleaning utensils," he shuffled through his notes.
"Now," he clapped his hands again, the room slowly returning to some quiet. "Before this little interruption I was just about to give out your next assignment. You will all be working on a presentation about the goblin rebellions from 1880."
The classroom collectively groaned and Regulus almost turned back to his paper when something caught his eyes. McGonagall had halted on her way outside.
She listened for a moment as Binns droned on about pairing up, and working for at least a few weeks on this and learning from it as much as possible. Then she stepped closer again and interrupted with a subtle throat clearing, "Professor Binns, if I am not completely mistaken this is your yearly revolution assignment, is it not?" Binns nodded, looking puzzled. "And you hold on to the practice of pairing up students with those one year above for this purpose?"
"Ehem, yes, certainly. It has many benefits, you see-"
Apparently Professor McGonagall was also not the biggest fan of Binn's everlasting lectures. "Yes thank you. I have a proposal: how about we, how shall I put this, mix things up a little?"
If he hadn't already been a ghost, Binns would have probably had a heartattack just about then. "M-mix things up? But Minerva-"
"Oh," she made an impatient hand gesture and Regulus was starting to gather the distinct impression that she had something very specific in mind, "your assignments will still be done Cuthbert but how about we work a little on the interpersonal relationships between the houses?"
"Well, I'm really not certain if that-"
"How about we pair up my Griffindor eight year students with the seventh year Slytherins this time?"
Regulus allowed himself a tiny little smirk as he saw the absolute outrage on his brother's stupid face. It looked like he was about to argue but then the words seemed to freeze in his mouth when she turned slightly towards her two students.
"In fact," she said, as if the thought had just occurred to her, "these two should be absolutely perfect candidates for the job."
Regulus didn't like where this was going.
"Minerva ..." Binns tried once more, but it was clearly a lost battle.
McGonagall seemed to think so too, because her eyes flickered over the sea of students and landed on someone in the backrow.
"Mr. Rosier is it?" there was a grumbling response and even though they sat rows behind Regulus could practically feel the tension enter Barty's body. Like always when someone talked to Evan. Or looked at him. Or breathed in his direction.
Regulus wasn't sure why Evan deserved that sort of extensive protection, but he didn't really seem to mind.
"Are your marks halfway decent in history of magic?" Evan looked miserable.
"They are," he said nonetheless.
"And can you work with a Griffindor for a limited amount of time?"
"Uhh I suppose but-"
"Excellent. You will be paired with Mr. Black then."
Sirius started shaking his head at that. "Oh no no no, Minnie please don't do this to me, I-" but the absolutely murderous glare his Professor sent him, made him shut up.
The only one who could probably rival that glare currently was Barty, who sat on the edge of his seat, hands clamped around his table.
Under any other circumstances Regulus might have enjoyed seeing the nutter so riled up (not that that was particularly difficult to accomplish), but he still really didn't like were this was going. That feeling intensified when Professor McGonagall's eyes hefted onto him.
"As for you Mr. Potter," she spoke, eyes never leaving Regulus, "how about you work with the young Mr. Black?"
Oh Regulus really really absolutely definitely didn't like where this had gone.
To his horror Potter turned slightly towards him, smiled and then shrugged his shoulders. "Sure."
~~~
Regulus was seething.
Not only was he expected to work with a Gryffindor, he was expected to work with Potter. And not only was he supposed to work with Potter, he was supposed work on one of the most important assignments of the year with the guy.
To everyone's and his own surprise he made his displeasure known. Regulus's mind had always loved to argue. However Regulus himself was what his mother liked to call docile. There really wasn't that much fun left in arguing if you were usually met with a backhand.
But this matter had been so fucking frustrating he'd raised his hand and argued over house rules and loyalties, over family statuses and Black pride. And through it all Professor McGonagall had barely spared him the time of day, and James fucking Potter had smiled.
When Regulus had started to grasp at straws, telling his teaches that it would be nearly impossible for them to find a place to work together, since neither could enter the others common room, Potter had casually offered that they could use his room and that was that. Regulus had wanted to throttle him. Still did actually.
How was he being punished again, for something Sirius had done?
Regulus was quietly contemplating if and how the throttling might be arranged without getting into too much trouble, when he felt an elbow landing in his ribs not too gently.
"What?" he hissed and scooted away. He didn't like being touched. Even a bit of an elbow could do a lot of damage to a body that bore as many secrets as his.
Dorcas's grin was cunning. "This is bloody fan-tastic."
"Are you having a laugh?"
Dorcas tutted, then leaned back in mock-casualness. "My, my Reg, didn't you hear? You're paired with James Potter. The James Potter. Captain of the Gryffindor team, stealer of brothers, king of pranksters, need I go on?"
Regulus glared. "I'm going to find a way to avoid this, I'm going to-"
"No you aren't! I'm serious Reg haven't you been listening? They want you to go to his room. They want you in Captain James Potter's room ..."
Regulus looked at his friend in distrust. "So?"
"So?? So that's our chance! That's our way in to the minds of Gryffindor's. This is premium access Reg. McGonagall basically just handed us the bloody house cup."
"You want me to spy on him?"
Dorcas made an impatient sound and started shoving her quills into her bag, as Professor Binns ended the lesson.
"Cas, I can't bloody stand the guy. And I'm pretty sure he feels the same. His best fucking friend is my brother. The only thing I'm gonna do in his room is destroy it."
Dorcas shrugged, "fine by me. As long as you figure out their strategy and set up for their matches against us before hand, go ahead."
Regulus leaned back. Trapped his quill between his teeth before remembering his manners. It could work ... Potentially.
He wouldn't have to limit his snooping to Quidditch strictly. He could try to actually help 'the cause'. His stomach clenched as he thought about this. Would it be enough to give mother any information he extracted? Or would he have to step in front of the dark lord?
Maybe he should stick to quidditch.
If he got caught, everything was fucked anyway. No one would believe that Regulus Black was looking through golden boy James Potter's room for quidditch notes.
He'd be singlehandedly responsible for igniting the cold war that had been waging between the Blacks and the Potters for years.
So what, he thought bitterly. It wasn't like he could loose another brother to this.