Severus had always wondered. In his sixth year at Hogwarts, when he had first learned that Black was queer and fancied one of his friends, Severus had hoped that Potter was the object of Black's unrequited lust. That would have been too sweetly perfect - especially later, if one of his former tormentors had suffered over the other's marriage and death in the same way Severus suffered over the loss of Her.

He had watched them during their final schooldays together, hoping to find evidence to fit his theory, but he was never able to prove it. It seemed just as likely that Black wanted Lupin. But that was absurd. Black, with his looks, money, and charm, could have anyone he wanted. Why would he want a creature like that?

It was only now, years later, with the three of them thrown together by circumstances once more, that Severus had learned the unequivocal truth. There was no way to avoid it, with the old house's thin walls, and the room they gave him right next to Black's.

He hated it - staying at the house. Twelve Grimmauld Place. But sometimes it was necessary, when he needed a place to stay in London, or not to be found for a while. Black was grudging enough about the room, but although the house was his, it was also the Order's headquarters, and he had little say in the matter. That Severus had been given Regulus's old room was just the latest in a series of cruel jokes fate had played upon him.

They were at it again. Severus could hear them. Every sigh, every laugh, every moan, every ecstatic cry was crystal clear. He did not want to listen, and yet, night after night, he found himself with his ear pressed to the wall, hungrily drinking in the sounds of their passion.

He wanted neither of them. The werewolf, his body a patchwork of twisted scars, filled Severus with nothing but revulsion, and his contempt for Black was absolute after seven years of cruel schoolboy indignities. No, he wanted what they had. That Black, after everything that had happened, had got what he wanted, while Severus suffered and paid his debts, with no recognition for the sacrifices he made, was yet more proof, if he needed it, of the basic unfairness of the universe.

He wanted Black to know what it felt like to be on the other side of the wall, mocked by the nearness of that which could never be his. To wake alone, night after night, to those sounds, in that cold bed, in that damp house, hard and hopeless. But there was nothing Severus could do about it. Their passion - Lupin's and Black's - was beyond his control.

If Black did not sound so much like his dead brother when he was being fucked, perhaps Severus could have stood it.

Sometimes he caught himself staring at the spot on the room's hardwood floor where Regulus had once knelt, nearly two decades past, to suck his cock, the day after Severus had taken the Dark Mark and sealed his fate. Sometimes he imagined that the scent of the dead boy still hung in the air. Grey eyes haunted his dreams and he got no rest.

Severus ground his teeth together as Black begged the werewolf to fuck me - please - oh god, Moony - harder! Regulus had never done that - had never wanted it that much.

He tore himself away from the wall to lie on the bed, seething with a cold rage that was never far below the surface. For a while, he touched himself, hoping that a wank would afford him at least a few hours of dreamless sleep, but it was no good. The black hair and grey eyes of his fantasy kept turning from the boy Severus remembered into the man in the room next door, and his hands, roughened by years of exposure to harsh potion ingredients, gave him no relief. His balls ached for release, but he could not get there.

Severus gave a sigh of frustration. He would have to go. If he did not, he would get no sleep that night, and he needed it for his mission the next day.

Getting out of bed again, he went to his traveling case and took out a set of unremarkable Muggle clothing and a brown cloak. He dressed quickly, pocketing a tiny wooden box and a small silver flask, before hurrying downstairs and out the door.

Severus gripped his wand tightly under a fold of the cloak, eyes wary. There was a good chance that someone was watching the house, but they were unlikely to suspect that the figure dressed in denims and a brown traveling cloak was Severus Snape. Once he Apparated, they would have no way of tracking him.

The alley in which he rematerialised had no lights. Severus knew it well. He removed the cloak, folding it over his arm, and stepped out onto a cobbled street strewn with litter. The buildings lining it watched him with dark, empty windows - those that were not boarded up. It was a Muggle street, but still Severus hunched his shoulders against the prying eyes he imagined were always there, always watching. Some might call it paranoia, but his habit of wariness had kept him alive and out of Azkaban thus far.

Stopping at a house distinguished only by the light shining from a few of its windows, Severus knocked at the door. There were better houses. There was even a Wizarding one, though Severus had never been there. This was what he could afford, and here, at least, he could be certain that he would not be recognised.

The door was opened by a plump, tired-looking woman wearing a green dress. She frowned at him suspiciously. "What d'you want?"

"I've come about the wardrobe," he said tersely, giving the coded passphrase that would gain him entry.

She looked him up and down, and nodded, opening the door wider to let him in. "And what is Sir looking for this evening?" Her tone was warmer now, and more professional.

"A boy," Severus told her, keeping his voice low. "Young, but not a child. Seventeen or eighteen." He knew how young some of them were, and his gut twisted, remembering grey eyes again. Regulus had been fifteen, the first time.

He paid the fee for an hour of standard services, and the madam called in a boy for his inspection - a slender youth with dark eyes and too-large ears. His appearance was of no consequence.

"He'll do."

The boy bowed his head. "My name is -"

Severus cut him off. "I'll tell you what name to use."

He nodded and led Severus up the stairs and down a narrow corridor to a small and sparsely furnished bedroom. Turning towards Severus, his professional smile became a look of confusion when he caught sight of the wand in his hand.

"Imperio."

The Ministry of Magic might classify the curse "unforgivable", but Severus knew such things were relative. The boy was a Muggle and a whore. There would be no outcry on his behalf, in the unlikely event that anyone ever found out. His eyes slipped out of focus, and he stood, relaxed, waiting for instruction.

"For the next hour, your name is Regulus Black," Severus told him. "You will do as I tell you, and when you address me, you will call me 'Sev'. Do you understand me?"

"Yes, Sev."

Severus removed the silver flask and small wooden box from the cloak's pockets. Carefully opening the box, he extracted a single dark hair from the soft lock that lay coiled within. Uncapping the flask, he dropped the hair into the potion, then held it out to the boy.

"Drink this. All of it."

Without hesitation, the boy took the flask from him and tilted back his head, swallowing the thick potion in a few gulps. The transformation began almost at once. The ears shrank, the eyes lightened and grew a thick fringe of dark lashes, the hair lengthened and curled, the line of the jaw shifted subtly, and the lips became full and pink.

"Regs," Severus groaned, stepping forwards to bury his hands in silken black hair. He turned the face up for a kiss, tasting and biting for long moments, until the soft lips were tender and swollen, running his hands over the achingly-familiar body.

"Undress," he told him. "And then you may undress me."

The boy moved swiftly and obediently to do Severus's bidding. Something of his trade remained in his movements as he shrugged out of his dressing gown. The alluring sway of his hips, the provocative looks he casts the older man. It was all wrong.

"No." He grabbed the boy by the shoulder, squeezing hard. "Not like that."

He hated that he had to tell them how to be Regulus. It spoiled the mood, acknowledging what their dynamic had truly been.

"I am going to fuck you," he said between gritted teeth. "You will allow me to do it, but you don't want it. You don't enjoy it. You will let me do it because you're afraid that I will hurt you if you displease me, and because you've convinced yourself that the attention I give you means that I care for you."

She had never been afraid of him, and he had never wanted Her to be. She had been bright and passionate and alive to his touch, and he would never have dreamed of hiring a whore to wear Her seeming, even if he had had the means for it. She was a goddess to be worshipped, while Regulus had only ever been a proxy for the punishment and degradation Severus wished upon his brother.

The boy with Regulus's face cast his eyes down as he pushed his pants over slim hips, letting them puddle on the floor at his feet. When Severus put a hand on his shoulder, silently urging him down, he knelt, and with no more than a quick, shy glance up at Severus, went to work on the fly of his denims with deft, familiar fingers.

"Hurry," Severus hissed.

He was rock-hard just looking at the bowed head and tender neck, and had no wish to waste his hour on trivialities. He pulled off his jumper and teeshirt as the boy tugged his trousers down to the floor, then stared up at him expectantly with those wide, grey eyes, awaiting his next command. His posture was so thoroughly submissive that Severus's cock gave a throb of longing. Tangling his fingers in the silken hair, he pulled the boy's head roughly towards him, forcing the softly parted lips to take his cock.

"Deeper," he muttered, and the boy complied, licking and sucking and swallowing him down, until the wiry black hairs at the base of the shaft brushed his nose.

His mouth was hot in a world of cold, and his tongue was the best thing Severus had felt in months. He wanted it to go on forever, but knew that if the boy kept at it much longer, he would finish too soon. More than half of the hour he had purchased still remained.

Severus tightened his grip on the boy's hair, pulling him away, urging him to his feet. "Kiss me."

The mouth on his was tentative, uncertain. Severus forced it open, tasting him deeply, roughly, before pushing him away, shaking him.

"Why?" he demanded. "Fool! Why go off like that and let yourself be killed? What did that accomplish? You should have stayed and kept your mouth shut. I could have kept you alive."

Regulus's face stared back at him, wide-eyed and fearful, but the boy who wore it had no more answers for him than the last, or the one before him. "I'm sorry, Sev," was all he could say.

But "sorry" was not good enough. It could never make up for all the years of rage and guilt Severus had suffered after Regulus's disappearance.

"You never should have joined," he spat, grabbing the boy's hand and yanking his arm into the light to expose the skull and snake tattoo on the pale skin of his forearm. "You never had the stomach for the work. All you saw was the glory. Get on the bed."

Wordless, tense, the boy moved to sit on the mattress. Severus followed.

"Lie down," he commanded.

He ran his hands over the familiar, compliant body, touching every curve and hollow and secret place. Eyes that once belonged to Regulus watched him all the while. Bending his head, Severus tasted the soft skin of his belly, breathing in the scent which Polyjuice potion recreated only imperfectly. His hand closed around the perfect little cock, stiff and ready, waiting just for him.

"Mine," he growled, tightening his grip. "You're mine forever now, and no one else can have you. Say it."

"Yours," the boy gasped, back arching. "Yours forever, Sev."

He stroked the small, sweet cock for a moment, enjoying the sight of the foreskin rolling over the head, as the boy's breath came faster. At last, he took his hand away.

"Turn over. On your hands and knees."

There was a bottle of lubricant on the nightstand, beside a bowl of condoms. Severus squeezed some of the slippery stuff out onto his fingers before roughly shoving those supple, hairless thighs apart and settling himself between them. He ran his slick fingers down the cleft, prodding at the tight hole, tense and closed with the fear he had commanded the boy to show him.

"Do you want it?" he asked.

"I - you said -" the boy stammered, confused.

"I know what I said," Severus snapped, running his well-lubed fingers over his erection, readying himself. "Tell me."

"You can do anything you want to me, Sev," the boy whimpered in Regulus's voice. "I'm yours."

"And if I think you deserve to be punished?"

"Then you can punish me."

"I will," he said, pressing the tip of his cock hard against that perfect, puckered hole. "You deserve it for running off Merlin knows where, and getting yourself killed," he went on between gritted teeth as the head forced open the tight ring of muscle. "For being a fool and a fucking idealist. For never telling me where you were going or what you were doing. For deserting me when I might have saved you."

Shoving hard, he buried himself in the narrow passage with one swift, punishing stroke. The boy gave a cry of pain, pulling away instinctively, but Severus grabbed him by the shoulder and held him steady. He took his time, drawing out the moment, pausing between thrusts to hear the whimpering, panting sighs of the boy who felt like Regulus, clutched hot and tight around him.

Regulus had meant nothing to him in life, so how was it that he held so much power over him in death? Was he truly still punishing Regulus for leaving him? Or was Severus only punishing himself for his inability to save anyone who mattered? He fell against the boy's back, pressing him flat to the mattress, fucking the ghost of Regulus Black with all the power of his pain and his rage and his despair, until he came, jerking and bucking and calling out to a lover seventeen years dead, still feeling his hold, tight around his cock.

When he came to rest, he could feel the boy's body trembling beneath him. He withdrew, turning him over. Regulus's face stared back at him, eyes wide with pain and fear, lips bitten, cheeks wet with tears.

Severus lowered his eyes, ashamed.

Regulus had never deserved any of it - not the way Severus used him, nor his fate at the hands of the Dark Lord. He had been an innocent.

"I'm sorry, Regs," he whispered. "Don't -"

He pressed his mouth to the bitten lips, but they barely responded. Remorseful, Severus kissed his way down chest and belly to nuzzle at the limp penis, taking it in his mouth, trying, belatedly, to offer a little pleasure in return, but to no avail. Regulus had never wanted that, either. All he had ever wanted was affection - to be held and loved.

Severus realised there were tears on his own cheeks, too, and he dashed them away, crawling back up to lie beside the boy, gathering him into his arms, holding him close. "I'm sorry," he said again, tearfully, and kept saying it, cradling the silent boy to his chest as if he were something precious after all.

When the body in his arms began to shift and change, Severus knew that his hour was up. He retrieved his wand, performing the Cleansing charms before raising it to the boy's face.

"Obliviate," he said. "You will remember only that you came to this room with a man who fucked you. Nothing out of the ordinary happened. You will not even be able to recall his name."

Blank-eyed, the boy nodded.

Severus dressed quickly and descended the stairs without another word, giving the bored madam no more than a curt nod of farewell before leaving the brothel, as empty as he had arrived.