Humanity's obsession with sex was well documented and when Cas had first taken a vessel to walk the earth, he had been warned repeatedly about not succumbing to its siren-like call. He'd mostly resisted, except for one or two minor incidents that were hardly worth mentioning. So he couldn't explain what had prompted his attempt to engage Dean in a sexual relationship. The hunter had always insisted that he was absolutely, one hundred percent heterosexual. Cas knew this to be a lie, and Sam had hinted as much from time to time, but if Dean were determined to drown in denial, who was he to try and force the issue?

And then he'd allowed Lucifer to ride in his vessel for a while and it had opened his eyes. He hadn't expected the ruse to work for long, Lucifer's impression of him was laughably bad and he figured it wouldn't take more than a day or two for one of the Winchesters to realize he wasn't himself anymore. But he hung around for months, behaving outrageously out-of-character and it was only when Lucifer's own patience snapped that Sam had realized the truth. It was the final straw.

He'd decided that enough was enough. He'd given everything, sacrificed almost everything for Dean Winchester, and he was no longer happy to sit and wait for the hunter to realize that Cas loved him. His plan was simple, present Dean with a sort of fait accompli, that he'd have no choice but to help Cas when he asked for it because he was Dean's friend and who else could he ask? He hadn't expected the curve-ball of Dean suggesting he approach Sam instead.

The look in Dean's eyes when he said it told the whole story. He expected Cas to refuse. He wanted him to be humiliated by the suggestion and just shut up and go away. Cas was done with it. And so, with little expectation that Sam would have the slightest interest, he nonetheless resolved to discuss it with him. If Dean wanted to see him ask Sam for sex, he'd do it and damn the consequences.

And what consequences! Sam had agreed, and relatively enthusiastically, which had been a surprisingly welcome development. But as good as it felt, and as willing as Sam was to allow Cas to be the one in control, Cas had quickly realized how badly he'd blundered. He didn't want Sam, whose submissive tendencies were too much for Cas's inexperience and he found himself overcompensating. Hurting Sam when it wasn't necessary, to the point where Sam's capitulation to increasing levels of humiliation and pain were more important to his pleasure than Sam's own enjoyment. That he could soothe any injuries with his Grace seemed to be beside the point.

He might not have had much experience with sex. But he'd watched humanity for millennia and he knew that they were on a destructive spiral even before that first disastrous decision to move their activities out of the bedroom and into more public areas of the bunker. But by now, this affair had seemingly taken on a life of its own, and Cas felt no more in control of it than Sam. All he knew was, that first time Dean had walked in on them, his body had reacted instantly to his presence.

Because despite his anger and his frustration, it was still Dean he wanted. And it was fucked up, to use one of Dean's saltier expressions, to get aroused from Dean watching him with Sam. But as soon as Dean had fled, so had his desire. He'd shoved Sam aside so roughly he'd hurt him, slamming his head into the table and giving him a concussion. That should have been a wake-up call. Instead, he grimly healed Sam and wiped his memory of the entire encounter, just to be safe. If Sam noticed a curious blank spot in his mind, he never called Cas on it.

But the idea of Dean watching as he climaxed became an obsession. A twinge of conscience had him considering masturbation, if he could engineer Dean walking in on him going solo. But there was another element that he hadn't considered before now. Dean was in pain, that much was clear. He hated that Sam and Cas were fucking and it was driving him to drink and despair. And yet, he still stubbornly refused to admit the truth. That he loved Cas and wanted him.

The only solution was to up the ante. He had to force Dean to face what was happening, and break down the walls that were keeping them apart. It occurred to Cas that what he was planning was not very fair on Sam, but he had no doubt he'd be forgiven. He'd done far worse in the past, and yet they had remained friends.

His jaw set, the plan was made. He'd seen Sam entering the library earlier and that was an excellent place for what he had in mind, since it would neatly bookend the previous time Dean had walked in on them. Sam was there, staring listlessly at his computer. Cas considered him for a moment. Sam didn't look good, his hair was lank and stringy, his face was pale and there were dark shadows under his eyes. He hadn't noticed during their encounter this morning, but Sam's room had been quite dark.

"Sam," he said and it was not comfortable that Sam flinched at the sound of his voice.

"Cas," he croaked, raising his eyes hesitantly. "I uh, again? So soon…" He shook his head and shoved away his laptop. Cas sat down in the chair he'd selected as to provide the best view from the door, and opened his pants.

"I want your mouth on me, Sam," he instructed. Sam dropped to his knees and obediently shuffled forward, bracing himself against Cas's thighs and dipping his head. He licked his way up the shaft of Cas's cock and then enveloped the head in his mouth. Cas groaned, he really needed to get Sam to do this more often. Sam continued this slightly teasing, light sucking and licking movements that quickly reduced Cas to a quivering, gasping wreck. All thoughts of his plan had utterly vacated his mind, he could focus only on the gorgeous sensation of Sam's mouth and tongue.

Sam flicked a look up at him and Cas met his gaze as he slowly and deliberately swallowed Cas's cock down until it butted against the back of his throat. His body rebelled slightly and Cas infused him with a whisper of Grace to tamp down his choking reflex. Sam shivered and began to fiddle with his jeans, freeing himself from their confines and wrapping one hand around himself. He began to hollow out his cheeks as he sucked, Cas's hips bucked in response and he thrust his hands into Sam's hair.

A choked-off exhalation of breath was his only warning that Dean had entered the room. He opened his eyes lazily to Dean standing there, laptop in one hand and the other straying unconsciously to his crotch. His mouth was open and his eyes were dark, pupils blown wide with lust but shadowed with anguish.

"Yes, Sam," Cas encouraged, locking his eyes on Dean. "That's good. So good." And it was. Knowing Dean was there, watching this flagrant display of sexual congress and unable to summon up the will to leave sent sparks of arousal along his nerve-endings. Almost overcome with the heady sensations of power and desire, his head fell back and his eyes drifted closed. His orgasm slammed into him and he cried out as he spilled into Sam's throat. Sam shuddered and sobbed as he quickly followed Cas over the edge. Cas's eyes slowly opened to see Dean running out of the room.

Sam pulled away from him, wiping one hand over his mouth and then looking down at the mess he'd made on the floor in dismay. Cas made an idle gesture to dismiss it, and Sam fastened his jeans and levered himself up off the floor. He didn't look at Cas, his movements were quick and jerky, and Cas had the feeling that Sam had something he wanted to say. But he remained silent and instead hustled out of the library as fast as he could.

Had he seen Dean? It seemed unlikely from his angle and surely that would have pushed Sam into some kind of angry outburst? Cas adjusted his clothing and stood up. He had a translation he needed to work on and he really needed to not think about sex for at least an hour or two. And maybe not think too hard about what he was doing to Sam.

Of course, his plan assumed that Dean's reaction to seeing him with Sam would be anger. He hadn't banked on miserable resignation. The conversation the hunter initiated with him in the war room had been little short of surreal, and learning that Dean had overheard his initial approach to Sam in the library meant that it was Cas whose temper finally ignited. Dean would break down and confess if it killed him.

He was spinning out of control, and a strange, detached part of him seemed to know it. Lucifer had laughed at his self-restraint, mocked it and tempted it with illusions of Dean to the point where Cas had seriously considered ejecting himself from his own vessel. But Lucifer had the upper hand and all Cas could do was grit his teeth and hope it was worth it. It hadn't been. Lucifer had lied about his ability to fight Amara, and when she'd captured and tortured them, he'd spinelessly forced Cas to the forefront, making him take the brunt of her anger and sadism.

Such memories made Cas retch and he pushed them aside. He had a mission to fulfill. He strode down the hall to Sam's room, where he'd arranged for Dean to arrive a little later. He walked into Sam's room without knocking and Sam came up off the bed, a defiant tilt to his head.

But he didn't say anything, just shed his clothes robotically and climbed onto the bed on his hands and knees. His head hung down, his hair like a curtain and there was a sound like a suppressed sob. As Cas discarded his own clothing and moved into position, Sam spoke.

"No more," he said. Even with his celestial hearing, Cas could barely hear him. "After this, we're done." Cas's temper flared once more. He was close to achieving his goal, how dare Sam try to deny him what was his.

"No," he said firmly. Sam looked over his shoulder at him, frustration baring his teeth. Cas couldn't stand it, he pushed Sam's head away. But Sam had found some semblance of his dignity at last and wouldn't be denied. He demanded an explanation and Cas gave him the only one he could, which was that he was in charge, they had already established this and Sam couldn't back out now just because he was getting cold feet.

And so Sam fought him. He'd never done that before and for a moment Cas had been too shocked to react. He didn't mean to be rough, he certainly didn't mean to force his way into Sam's body with too little preparation. And yet, when he did so, those damned submissive instincts kicked in and all the fight drained out of Sam. He sagged a little, and Cas pounded into him mercilessly, punishing him for his failed rebellion.

When Dean knocked on the door, calling out his brother's name, Sam had frozen. Cas slapped him on the ass, reminding him who was in charge once more. And then the door opened and Cas had to struggle against the urge to stop and throw Dean out. Because he could feel Sam's distress and it was infectious. Determined not to be thrown off course, he grabbed savagely at Sam's cock and pumped it with his hand, even as his legs began to shake as his climax threatened. His eyes never straying from Dean's gaze, he ejaculated into Sam and moments later felt Sam come messily over his hand. Sam had actually howled as he did so, a sound that seemed to be both pleasure and pain all at once.

He was prepared for Sam to start fighting him again and he held him tightly in position as he continued to stare at Dean. The hunter's face was horrified, his eyes empty pools of black despair and yet he still didn't seem to want to challenge Cas on what he was doing. He backed away slowly and closed the door with a click.

No, instead it was Sam who was angry, Sam who yelled and screamed and wept as Cas explained how they'd gotten to this awful place. As it dawned on Sam that he was little more than a pawn in Cas's bigger game to entrap Dean, something within him seemed to break. Something Cas wasn't sure he could fix. But they were close to the end now, the angel was sure of it. Sam was tough, he could withstand this.

But Sam was afraid of him now. That was new. He'd been afraid of him once before, when they'd first met and Sam had been hiding his demon blood addiction from his brother and from Cas. But he'd been afraid then because he knew he was in the wrong. Now he was afraid of Cas because he no longer trusted the angel to have his best interests at heart. That really ought to have been more painful than it was, Cas thought. Sam had been a good, loyal friend and in many ways a better friend than Dean over the years. That he thought nothing of sacrificing that friendship in order to bring Dean over to his way of thinking should have disturbed him more.

What had he lost to Lucifer, when the archangel had inhabited his body and his mind? Or was that laying the blame on an easy scapegoat when the truth was, Cas had allowed himself to be corrupted. By the world, by Dean, by the temptations of power and easy answers. His Father, so long a paragon in his mind even when he'd lost faith in Heaven and it's motivations, was as lost and fallible and morally weak as humans and angels and demons, only with limitless power. Cas had lost his faith in his Father too. And now he'd lost his faith in Dean.

Snarling at himself, he headed back to the library. He was losing focus with this ridiculous introspection. And he still had a translation to finish.

Unfortunately, it quickly became clear that his concentration was shot. Nothing was going to get done until he'd finished this insane dance of seduction and abuse. So when Dean dashed into the room, his eyes bright and slightly crazed, he began to wonder how much control he really had over events. Whatever he saw on Cas's face, his expression dropped and he silently poured a glass of bourbon and slumped into a chair, drinking and not looking at him. And then Sam appeared, walking stiffly and his obviousness over sitting as far away from either of them as he possible could caught at Cas's throat. Damage was radiating outwards, like ripples on a pond. Cas had thought he had everything neatly managed, that he could contain the fallout of what was happening. It wasn't the first time he'd allowed his arrogance to overrule his good sense.

Dean had blurted out some rambling speech about how he wanted Sam and Cas to be happy together and it was plain that the hunter was making plans to leave. He might as well have screamed it in their faces. Frustrated, Cas watched him fade out of the room like a cheap special effect and in a fit of pique, used a tendril of Grace to steal his car keys.

Sam was sawtoothed and feral, his fury exploding on Cas in a way that the angel felt was a little unjustified. Nobody had forced Sam into this, not really. He'd wanted to be mastered and Cas had done it, and now he was complaining? He ordered Sam into the kitchen, placing the keys on the counter and then shoving Sam into the table. Sam had struggled, not holding anything back as he tried to resist, but he really stood no chance and it was almost cute how he snarled and thrashed as Cas calmly told him what he wanted.

When he ordered Sam to strip and he outright refused, it was clear this insurrection needed to be crushed. A little struggling was arousing, this on the other hand was infuriating disobedience. He ripped Sam's shirt from his body and the fear flared in the hunter's eyes. He'd moved quickly to remove his jeans then, standing there shivering with cold and fear. Cas felt his lips curl up in a smile. Sam's hands tried to cover himself, but Cas was having none of it. He smacked the treacherous limbs away and dragged Sam's head down for a kiss.

They'd never kissed before. Sam had been adamant that kissing was reserved for loving encounters and what they had didn't even begin to approach that. Cas hadn't minded, it wasn't what he was seeking anyway. But now his determination to discipline Sam meant crossing another of his boundaries. Sam melted, much to Cas's surprise. But it was delightful, and he felt real desire begin to build inside Sam, in a way that had not been so easy since their early adventures into sex together.

His original purpose forgotten, he focused on Sam's pleasure, Sam's needs. Cataloged the sounds he made and the reactions of his body as he teased and explored him. Why had he waited so long to do this, when Sam was so willing? Why had he focused his energy on Dean, who could never be this open when Sam had been there all along? This time, perhaps for the first time, there was something more to the sex than a race to the finish line. He made love to Sam, sweet, gentle Sam who undulated like a wave beneath him.

If Dean hadn't returned, things might have turned out differently. And Cas had designed that, even if he'd lost sight of it along the way. But there he was, stood open-mouthed and hurt and visibly aroused and Sam was back to being a convenience, a tool. And then not even that, as he climaxed screaming Dean's name, not Sam's. He didn't notice that Sam had reached his own summit. He hadn't even realized Sam was moving until he shoved Cas away from him, yelling incoherently. He stared at Sam, uncomprehending before his gaze drifted back to Dean.

Dean sagged against the doorframe and whispered to him. Cas wanted to weep as the hunter broke down and confessed in a tsunami of love and pain and self-recrimination. He needed Dean to see the damage he'd caused with his recalcitrance and selfishness. And then they'd come together, the love that should have blossomed between them long ago finally spreading its petals. But the peace Cas had sought for so long was short-lived. Dean dropped the bombshell.

"Cas, I… I can't do this. Not when my brother's uh… body fluids are still drying on your clothes."

Cas had considered this a minor annoyance, cleaning himself with a flare of Grace and moving in for another kiss. But Dean wasn't done it seemed, insisting that they had to make things right with his brother before they could move forward. Cas wanted to scream in frustration. Sam would be all right. Couldn't the apologies wait? He'd been so patient, why couldn't he have even a taste of what he wanted from Dean?

But what could he do? So he agreed and offered his opinion that he owed Sam an apology. Dean hadn't seemed as impressed with that as he should have been, after all hadn't Cas suffered too? But you couldn't talk Dean out of defending Sam, even when he didn't deserve it. So he hinted at being able to offer Sam some recompense, something to make up for what he'd been through these last few weeks. It was a lie, and not one he felt good about. But he couldn't imagine what Sam could possibly want except…

Except the sex on the kitchen table had been incredible. Better than anything they'd done together previously. Cas had felt emotionally engaged as well as physically aroused and the payoff had been better than he had imagined. He tilted his head at Dean as his mind raced. Would Dean agree to share him with Sam? It was the perfect solution to the problem, and Cas was confident in his ability to keep up with them both.

"What are you gonna do?" Dean said.

"It's up to you of course," Cas said carefully, aware that a single misstep could backfire badly. "If you insist on exclusivity then I'll think of something else." Dean's eyebrows skyrocketed and his face was disturbed. "What would you think of sharing me with Sam?"

"I- You- What?" Dean stuttered.

"I'd like to keep having sex with Sam if you don't object. This way he will feel less used and more appreciated," Cas explained. "We don't have to do this as a threesome, if that makes you uncomfortable."

"Are you insane?" Dean screeched. Cas pursed his lips. This was not the reaction he'd been hoping for.

"I hope not," he said quellingly. "I'm trying to do the right thing here, Dean."

"The right thing…" Dean looked dazed. "Do you think this is the right thing? You think this is what Sam wants?"

"I believe it is," Cas said.

Dean wiped a hand over his face. "I gotta tell you, I'm not keen. But, maybe you're right. I mean, I already had to deal with the idea you two were fucking. Why should I object now?"

Cas grinned at him, delighted that he'd seen reason. "We should go and speak with him immediately."

"Yeah, sure," Dean said. His voice had taken on that hollow quality again and Cas frowned at him.

"Your feelings come first," he reminded the hunter. "If you don't want this, tell me now."

"It's OK," Dean said. "At least for a while."

Cas dragged him down the corridor to Sam's room where he was sure to be sitting and sulking. Soon everything would be all right, Sam would see that he was more than a means to an end and Dean would love him and all would be right with the world. They could go back to hunting and saving people, only this time their nights would be filled with love and passion. Cas had managed to amaze himself, this really was the perfect solution.

He tapped on Sam's door and on hearing no reply, opened it to see Sam sitting on his bed, hunched over with his back to the door.

"Sam?" Dean said hoarsely.

Sam tucked something away under the mattress and then turned to face them. His face was blotchy and it was clear he'd been crying. Cas felt sort of bad about that.

"Sam," he began. "I'm sorry. I've not been as solicitous of your feelings as I should have been and I know right now you are feeling used and worthless."

Sam looked away, but didn't speak.

Undaunted, Cas plowed ahead. "Dean and I discussed it and we think, if you are agreeable, that there is no reason why we can't continue our sexual liaisons even if Dean and I are also in a relationship."

Sam just stared at him, his eyes dull and he showed no sign he even understood what Cas was saying. Cas looked at Dean in consternation.

"Sam, if you don't want this, that's OK too," Dean said, uncomfortably rubbing the back of his neck. "Cas just thought maybe it was mean to dump you like you don't mean anything and I… I'm OK with it if you are. Not together or anything weird like that. Just… sometimes he'll be with me and sometimes with you."

"OK," Sam said in a low inflectionless voice.

"OK? Uh, OK." Dean seemed at a loss for words.

"Maybe you'd like to think about it," Cas said kindly. "There's no need to give us answer immediately. Sleep on it and we'll talk about it tomorrow." He began to back out of the room. "Come on, Dean."

Sam looked up and nodded, before turning away. Cas closed the door and met Dean's gaze.

"He's very upset."

"He has a right to be, Cas," Dean said.

Cas's mouth thinned with irritation. There was that slightly accusatory note in Dean's voice again. But he kept his mouth shut, he was tired of the fighting. He leaned forward to kiss Dean, feeling that he'd more than earned it. Dean opened to him, sweeping his tongue inside Cas's mouth and Cas thrilled as everything he'd worked for was finally within his grasp. He was only vaguely aware of a faint clicking sound but Dean went rigid and pulled away from him.

"What was that?" His tone was sharp and Cas really felt it was an overreaction to such a tiny noise. He looked around for the source of the sound.

"I'm not-"

A gunshot interrupted him, shattering the peace of the bunker forever.