This is another cross-posted fic from AO3, and (as of this original posting) it's several chapters ahead, so if you can't wait, you can search it out over there.

Content Warnings for some child abuse, homophobia, and talk about sex.

Chapter Summary: A run-in with his little brother leave Sirius shaken enough to do something stupid and terribly cruel.

"Regulus! Reg, wait! Please!"

Sirius stumbled down a staircase, barely avoiding one of the vanishing steps as he ran. Ahead of him, his brother showed no signs of stopping or even slowing down. Swearing under his breath, Sirius jumped the last two steps, hit the corridor and sprinted.

"Regulus, stop! "

The younger Black brother had just reached another set of stairs when Sirius caught a handful of his robes and yanked him back.

"Let go of me!" Regulus snapped and thrashed in his brother's grip but Sirius was taller and desperation gave him a burst of strength. The corridor and both staircases were blessedly empty. Most of the students were either camped in the library studying for their very last exams, or had escaped to the warm, sunlit grounds. However, Sirius had just learned better than to trust the security of empty spaces.

Still holding tight to Regulus's robes, he caught sight of a familiar tapestry. Sirius used his free hand to pull the edge of the wall-hanging aside and shoved Regulus through the archway hidden behind it. Regulus staggered a few steps down the hidden passageway before catching himself against the stone wall.

Sirius let the tapestry fall closed behind him, plunging them into darkness before he pulled out his wand and hissed "lumos." By the light that shone from his wand tip, Sirius found his younger brother glaring at him, full of anger and confusion. Sirius raked a hand through his shoulder-length hair, trying to mask the terror thumping in his chest with agitation.

"Listen, Reg, I know what you think you saw—"

"You were kissing him, Sirius! Snogging him—a boy!" Regulus snarled, thankfully quiet. He had hoped Regulus had only caught a quick glimpse before bolting, something Sirius could pass off as anything other than what it had been.

"It wasn't what you think…"

Regulus didn't reply, instead he very pointedly raked his gaze down Sirius from head to toe. It wasn't until that moment Sirius realized exactly how he must look. His hair was tangled, robes hanging open, shirt untucked and rumpled, tie long forgotten on the floor of that supposedly unused classroom, and the top button of his trousers undone.

"Fuck," he swore under his breath and tugged his robes closed to hide the rest of the disarray. There was no hiding the swollen look of his lips though, or the love bite he could feel stinging on his neck. Damn Patrick Sutcliffe…who could have guessed a Hufflepuff would be so aggressive? Not that Sirius had minded, at least until his brother had opened the door and caught an eyeful of Sirius's greatest secret.

"It's—it was nothing," Sirius sputtered. "Just…part of a prank."

Regulus frowned and looked his brother in the eye again. Doubt flashed like steel in those familiar grey eyes. Doubt…and revulsion. Sirius flinched and pulled the edges of his robes tighter together. This was what he'd been afraid of.

After James had found out and been so accepting…so downright supportive, Sirius had dared to dream it might not be the end of the world if more people knew. Now the truth was staring him right in the face, and he realized exactly how much of a delusion those hopes had been.

"It was nothing, Reg." Sirius repeated, imploring his brother to believe him. "Just another stupid prank."

Regulus's frown deepened, but the repulsion in his eyes relaxed just a bit. He wanted to believe, Sirius realized. It was such a relief that Sirius burst out laughing, which seemed to put Regulus even more at ease. Regulus wanted to believe any excuse Sirius could give him, even a flimsy, nonsensical one.

"Just a prank?" Regulus asked uncertainly. Sirius nodded jerkily.

"Just a prank…I swear that's all it was…" Sirius lied with a shaky smile.

Regulus nodded slowly, still considering. "I…I don't get the joke…" he said quietly.

Sirius forced his smile wider, forced his hands not to shake. "That's because you're not the one being wound-up." Sirius was almost amazed by how calm, how confident his voice sounded. He certainly didn't feel it. No, beneath the hastily erected façade, he was panicking, crumbling.

"Don't worry about it, Reg," Sirius said. "Just…don't tell anyone."

Uncertainty darkened Regulus's eyes again, but he nodded. "I won't."

"Promise?" Sirius hated himself for asking, for all but begging.

"I promise," Regulus said. He shifted uncomfortably from foot to foot for a moment, his gaze drifting away from Sirius to the tapestry covered archway behind him. "Can I go now?" He asked.

"Oh—uh, yeah, of course…" Sirius stepped out of the way. "I—I'll see you on the train then?"

"Yeah…see you…" Regulus said as he brushed past Sirius and shoved his way out of the secret passageway.

The moment he was gone, Sirius's knees buckled. His wand fell from suddenly limp fingers and clattered against the stone floor, the light spell going out as it rolled away, leaving him in near total darkness.

What had he been thinking? He should have learned his lesson back in February when James had caught him snogging Bartleby Ibbott further up this same passageway. But no, he'd been careless enough to let Sutcliffe stick a hand down his trousers to celebrate getting through their Transfiguration O.W.L. They hadn't even remembered to lock the damn door.

"Stupid, stupid randy bastard," he muttered, not sure if he was cursing himself or Sutcliffe.

Now Regulus knew. He'd accepted Sirius's lies and promised to keep the whole thing a secret, but he knew. Sirius hadn't admitted his proclivities to anyone except James and a small handful of other boys throughout the school who shared them. He hadn't even told Remus and Peter, but now his Slytherin little brother, of all people, knew. Regulus was the last person in the entire school that Sirius wanted privy to his secrets, especially that one.

Not that there was anything he could do about it now. He could only hope Regulus would keep his word.

Still in the dark, Sirius pushed away from the wall, though his knees still felt a bit wobbly. He rebuttoned his shirt and trousers in the dark, straightening both as best he could while he debated if it was worth to go back and find his tie. Sutcliffe would be long gone by now, probably praying Regulus hadn't recognized him by the back of his head. Sirius knew he should find the Hufflepuff boy and apologize, or at least let him know Regulus wouldn't tell anyone about what he'd seen. In all honesty though, Sirius had no desire to see the other boy again. Not any time soon, at least.

When he was fairly certain he was as decent as he was going to get without a change of clothes and a few charms to hide the love bite, Sirius bent down to feel around for his fallen wand. He shuffled about the dark corridor for several minutes, swearing as he groped blindly for it before he realized it must have rolled out into the main corridor through the narrow gap beneath the bottom of the tapestry.

With one last curse, Sirius pushed back the tapestry and realized he'd been wrong; Regulus wasn't the last person in Hogwarts Sirius would want to know his secrets.

Standing a few feet in front of him, a foot resting on top of Sirius's wand, was Severus Snape.

"Lose something, Black?" Snape drawled. The toe of his shoe pressing down on Sirius's wand.

Sirius ground his teeth together as his eyes flicked between his wand and Snape's gloating expression. No interaction with the greasy-haired Slytherin could ever be considered pleasant in Sirius opinion, but this one was bound to be especially nasty after yesterday's events.

True, it had been James who'd done most of the hexing, but Sirius had helped, and he'd laughed at every second of Snape's humiliation. He didn't regret it either, though he had no desire to continue the spat right now. He was wandless and still shaken by everything that had happened with Regulus.

Snape's own wand was in his hand, tapping idly against his leg.

Pride won out over what little good sense Sirius possessed. His heart was still thundering in his chest, and a feral, thoughtless fear was pumping through his veins. Yet, Sirius drew his shoulders back and raised his chin, pulling on a mask of haughty boredom. Attacking always had been his go-to defensive strategy.

"Snivellus, you're looking especially greasy today," Sirius said with mock pleasantness. "Is it the heat or an overactive gland of some sort?"

Snape's lip curled, and his eyes flashed with anger, but he didn't rise to the bait. Instead, his attention shifted away from Sirius to the tapestry he'd just emerged from behind. Well damn, there went that secret passageway, and it'd been such a convenient way to get to Charms.

"Sneaking around the castle, Black? Planning another of your infantile little pranks, no doubt," Snape scoffed. Then his eyes were drawn back to Sirius and one eyebrow slid up his greasy forehead. "Or perhaps not…"

Sirius couldn't help the flush of rage and embarrassment that heated his cheeks as Snape took in his disheveled robes and the bruised love bite on his neck. His heart felt like it had jumped into his throat. He did not want Snape asking questions, not about that, because Snape would not fall for Sirius's badly constructed lies like Regulus had.

Faster than Sirius could blink, Snape's wand swept up in an arc and the tapestry behind him was wrenched to the side. The Slytherin frowned at the narrow, empty corridor stretching beyond. He'd been hoping to catch someone else hiding back there, Sirius realized, a smirk growing on his own face at Snape's look of frustration.

Sirius clicked his tongue in mocking disapproval. "Trying to play Peeping Tom, Snivellus?"

"Just checking to see what sort of slag would lower herself to fornicate with the likes of you in a filthy corridor."

"Spoken like someone who's only ever 'fornicated' with his wand hand," Sirius said. He was tempted to make a comment about Lily Evans leaving through the other end of the hidden passageway, but James was just as likely to murder him for that as Snape was.

Snape's eyes narrowed even as spots of red darkened his cheeks. He leaned forward, putting more weight on the foot still pinning Sirius's wand to the floor. Sirius tried not to wince as he imagined the wood groaning. Silently, Sirius promised to rain fire and destruction down on Snape's slimy head if the git damaged his wand.

"Or perhaps it wasn't a girl you were hiding down there," Snape said.

Sirius's heart skipped a beat.

He's just having a go at you! A thin voice said in Sirius's head. He only means it as a taunt, a baseless insult!

That rational voice did nothing to quell the sudden maelstrom of fear, anger, and shame Sirius felt rising within his chest, threatening to drown him from the inside out. He tried to keep his expression from betraying him, but Snape was nothing if not observant.

Snape must have noticed some small sign of Sirius's unexpected unease because he smiled cruelly and pounced. "You and those little friends of yours are always sneaking off, especially Lupin. Perhaps—"

"Fuck off, Snivellus," Sirius snarled, though his voice came out breathy and thin because he still couldn't breathe right. There was something wrong with his throat, with his lungs, with every organ inside of him.

The Slytherin boy's thin smile grew wider. "Touched a nerve there? Is this how you all get out of the castle?" He tilted his head to look down the hidden corridor again. "I've seen Lupin crossing the grounds in the evening sometimes…where ever does he go? The forest perhaps? Do you all get up to forbidden things in the Forbidden Forest? Tell me and maybe I'll give you your wand back."

Snape had been poking his enormous nose in their business for far too long. James had said as much only last month when they'd caught him lurking close to Gryffindor Tower after lights out. It had been the night of the full moon, just as it was now, and Snape had obviously been waiting for the Marauders, hoping to catch them doing something worth snitching to Filch or a professor.

Remus had already left for the Hospital Wing, and Sirius, James, and Peter had all been hidden beneath James's invisibility cloak, so Snape had come up empty handed, but James and Sirius had been plotting to teach the git a lesson about prying into their business. Sirius felt dizzy, but he refused to let it show, not in front of Snape. Instead he smiled, slow and vicious, because he had an idea that should scare the piss out of Snape and make him forget all the things he might think about Sirius.

"All right, Snivellus, you've got a deal…"