Needless to say, Dean was not happy about this.

If it hadn't been for Sam, there was no way in Hell- or more specifically, out of Hell- he would have put up with this. Lucifer walking free once had been bad enough. Admittedly, it was more what his presence had caused in apocalyptic terms, rather than his presence itself, but still... Nothing good could come of this. This was all going to go horribly wrong. The smartest thing in the world right now would be to stick an angel blade through Lucifer's chest, if only it weren't for Sam's adamant "you do anything to him, I'm gone" testimony that kept Dean's hands bound.

Where Sam had got the brilliant idea to fall in love with the devil, Dean didn't know. He'd known there was some... temptation. But Dean had thought it nothing more than an addictive power trip. Like the demon blood but in human (or rather, non-human) form. Sam was just crazed with the idea of the power Lucifer had once given him...

...and then he'd found said devil and his little brother in bed together.

That had, obviously, been a bit of a shock. After Sam had shown up, having dragged Lucifer from the depths of the cage through some absurdly complicated ritual driven by Sam's unwillingness to leave his acclaimed "other-half-he's-part-of-me-Dean-you-have-to-accept-that" behind, Dean had been obviously wary of what on earth Lucifer was planning to do with his little brother. Sam had insisted there was no intention with either of them for Sam to be his vessel once more, but Dean had been less than convinced. Lucifer had to be up to something. Lucifer was just taking his time, surely, to convince Sam.

Well, Lucifer had gotten inside him. Just not in the way Dean had been fearing.

Upon realising he was stood gaping in the doorway, Sam had shoved Lucifer off of him, rapidly pulling the covers over the two of them as he sat up, face painted red. "Can't you knock, Dean?!"

And Lucifer had just sat there smirking. Asshole.

After a stuttered argument with a furiously blushing Sam, it had become apparent that, despite his anger, there was very little Dean could do about this. So since that rather unexpected discovery, he had been a sulking presence around the bunker, avoiding eye contact with his brother and busying himself with work.

He didn't know where Sam and their unwelcome house guest were right now. Adamantly, Dean told himself he didn't care, occupying himself with rummaging through an old Men of Letter's box of supplies. Half of it was covered in dust, and he kept having to give things a thorough wipe with an old cloth just to figure out what they were. Not that it helped a lot of the time. There were spell ingredients in here he'd never even heard of.

Footsteps approached down the stairs behind him. Dean glanced over his shoulder, instantly scowling as he noted who it was, and turned back to the box in front of him.

"Good morning, Dean."

Ignoring the obviously sarcastic greeting, Dean pulled a rather worn old jar out of the box, squinting as he tried to read the label through the dust. He snatched up the cloth, scrubbing furiously at the layer of grime.

"You seem tense, Dean."

Dean scowled down at the object in his hands. "Look, just get lost, will you? Go bug someone else."

"Anyone would think you dislike my presence here, Dean."

Dean's eyes narrowed. He managed to scrub a clear patch on the jar, only to the find the label faded and too indistinguishable to read. "Course I don't," he muttered. "Cas doesn't either. Heck, I don't know what you did to Sam to get him to want you around, but no one else wants to you here."

With his back to him, Dean missed the minute shift of discontent on Lucifer's features. He looked almost upset. It was quickly covered, however. "That's because you are a brain dead imbecile, incapable of thinking of your own opinions outside of what you have been led to believe about me," he snapped.

Dean merely huffed. "Look, I ain't buying any sympathy for the devil crap, alright. Sam seems to think you deserve some kind of benefit of the doubt, but if it were up to me, you'd be either locked back downstairs, or better yet, dead."

"Unfortunately, you are not capable of doing either one of those things," Lucifer retorted.

Dean tightened his grip on the jar, opening his mouth to retort, when the grimy object slipped from the within his fingers and fell to the floor where it promptly smashed.

"Ah, great," Dean groaned, stepping back as a large poof of smoky substance drifted up in thick clouds that made him cough. He quickly stumbled back, covering his mouth, vaguely noting Lucifer doing the same. "That was your damn fault," he ground out.

Lucifer hardly seemed to be listening, still coughing a little and shaking his head as if to rid himself of the now receding substance lingering in the air. "What?" he muttered.

"You were putting me off," Dean insisted. Sighing, he knelt down and began collecting up the bits of glass. He had no idea what the contents had been, now just a pile of grey powder on the floor, but he was sure they could survive without it, so he scooped the lot up with his hands and dumped it into the bin.

All the while, Lucifer was just standing there watching him.

"You could help, you know," Dean grumbled, wiping up the last bits with a tissue.

Lucifer said nothing, turning his head languidly to the side and blinking a few times as if to ward off dizziness.

"Not even an apology," Dean continued, standing up and throwing the tissue in the bin with perhaps more force than necessary. "Didn't anyone ever teach you any manners?"

It was at that moment, that Lucifer nearly keeled over.

"What the-" It was pure instinct that made Dean catch him. Suddenly finding himself supporting two hundred pounds of archangel, Dean had the sudden urge to just push him off and simply let him fall to the floor, but some damnable nice instinct within him stopped him. "What the hell is wrong with you?" Dean snapped, grunting as he managed to maneuver the half-conscious figure into a nearby chair where he slumped against the back sideways. "Man, you're heavy."

One arm shakily grasping the back of the chair for support, Lucifer blinked, looking distinctly dazed as his gaze slid over to Dean, head almost lolling onto his shoulder.

"What?" Dean ground out, rather disturbed by the disorientated, blank look Lucifer was giving him.

"How did you get here?"

"What?" Dean frowned, drawing back slightly as his face scrunched up in confusion. What kind of twisted game was Lucifer playing now? "What do you mean 'how did I get here'? I live here."

"You do?" There was a kind of amazed innocence in Lucifer's voice, as if he'd just been told something incredible. "You're going to live where I am? Just like before?"

"What the hell are you talking about?"

Lucifer leant forward, nearly overbalancing, but managing to steady himself as he grasped the table with one hand. He peered at Dean as it transfixed by him, head tilting to the side curiously. "You said I disgusted you. You called me a monster."

"Er..." He probably had, he supposed. Though he couldn't remember doing so to Lucifer's face. Generally, he wouldn't have dared, though he'd got a little more confident recently, knowing Sam had strictly told Lucifer not to harm him.

"You said you didn't want to be anywhere near me anymore," Lucifer continued. He leant back, swaying, before leaning heavily sideway against the back of the chair. "It hurt when you said that," he mumbled.

"Okay...?"

"I couldn't change my mind," Lucifer continued, throwing one hand out vaguely to emphasize his point. It flopped weakly into his lap as if he couldn't quite control his limbs. "I couldn't. But I didn't want to fight with you. I never... ever wanted that."

Now severely baffled, Dean cleared his throat awkwardly. "Erm, okay, that's good, I guess."

Lucifer's gaze fixed on him, as best he could seem to manage, once more. "Does that mean you don't want to fight either?"

"Er... yes?"

Dean had thought there were many things Lucifer could do that would disturb him, but finding the devil now grinning at him like a child who had just been given a shiny new bike was not one of them.

"Really? You won't try and kill me anymore?"

Well... for the time being, he supposed... "I guess not?"

Seeing Lucifer suddenly reach out toward him, Dean drew back, expecting some kind of attack. What happened, however, was rather different, as he found himself being sloppily embraced by the being that had once beaten the crap out of him against his beloved car. "What the-"

"I love you, Michael."

...Oh. Lucifer now slumped against him, head resting on his shoulder, arms thrown around his neck, Dean held his hands awkwardly out either side of Lucifer's back, unsure what on earth he was supposed to do in this unexpected situation. Stabbing him came to mind, but there was neither an angel blade within reach, nor was this a valid excuse to give to Sam. Also, Lucifer kind of wasn't exactly being very threatening and deserving of it right now.

"Can... Can you just... get off of me?"

Obediently, Lucifer drew back, movements still unbalanced as he attempted to sit up straight in his own chair.

Dean watched this uncertainly. "Okay. Er, thanks..."

Silence fell. He didn't know what to say, let alone what to do. He could simply point out that he wasn't Michael, but there was never any telling what Lucifer would do, more so in a state like this. Besides... he'd never really seen Lucifer look so happy before.

"I really thought you were never going to forgive me," Lucifer continued suddenly, voice somewhat whimsical as he stared off at some vague point across the room. "You were still so mad, all the time in the cage."

"What?" Dean said before he could stop himself. "Michael- I mean, I was still mad in the cage? Like, the whole time?" Dean found himself frowning. He'd expected a bit of obvious friction after they'd first been locked away, but he'd supposed that surely some kind of at least temporary truce had been come to since. If you were stuck somewhere with someone for what you at least thought would be forever, it would seem a good time to stop holding grudges. No matter what Sam had done, Dean was sure being stuck with him would always be better than being apart. At least then they could sort things out, right?

"You were so mad," Lucifer mumbled. "Even when I tried to just forget it all, just for a while... I just wanted to talk with you. You said I'd lost that right. You said we couldn't be brothers anymore..."

Ouch. Dean knew what that was like, even if he'd known Sam hadn't fully meant it. And they'd made up. They'd fought it out and talked, and Dean was convinced that there was nothing that could happen between them that couldn't be fixed. You just had to try, right?

"You just wouldn't even try to talk about it," Lucifer said, as if he'd just read his thoughts. Heck, maybe he had. Angel powers and all that.

"Well, that was wrong," Dean mumbled. He had to admit, he had got that kind of vibe from Michael. He'd told the guy to get some counseling. That had perhaps been more appropriate advice than he'd realised. Michael had been a stubborn jerk. Lucifer was a stubborn jerk with his adamant hate of all things human. Dean hadn't realised, however, that with Michael, at least, he'd been willing to give a little leeway and at least try and talk things through.

"I still hate these humans," Lucifer muttered, brushing one fingertips shakily along the tabletop. "This earth has been ruined by them. I want them all dead." He paused. "But I want my brother back more."

Dean eyed him uncertainly. There was an obvious feeling of unease in his gut at Lucifer's bold proclamation against humanity, but pure fascination pushed it aside for now. "Did you ever say that to Mich- me?"

Lucifer gave a dazed frown in his direction. "Yes. You said you had to kill me."

"Why?"

"You said because it was right. Because Father said so."

Dean had to admit he didn't find that a very valid excuse.

Lucifer looked younger suddenly now. No longer fixed in a firm composure, no longer full of purposeful, controlled movements. Every word had been so carefully chosen before, but now they were just spilling out.

"I was just trying to do what I thought was right, Michael. I had to carry on on my own because you left me."

And, oh God... He sounded like Sam.

Sure, he was still warped, downright ruthless, and possibly kind of evil. But he was also a little brother. And maybe Dean had a thing about little brothers that just couldn't help but bring out a protective instinct in him.

"You know," Dean said. "I- I mean, Dean, was once told he had to kill Sam or save him. Did I ever have a choice like that?"

Slowly, Lucifer glanced up at him with bleary eyes. "You never tried to save me," he said.

Dean regarded him silently for a few long moments, before sighing, rubbing a hand over his face in frustration and wondering how he ended up in these situation. "Man..." He gave Lucifer a half-hearted glare. "I still ain't giving sympathy to the devil. But I'm not a fan of any big brother abandoning their little brother, either." He sighed heavily once more, holding one arm out. "Come here..."

When Sam and Cas returned, bags of groceries in hand, it wasn't surprising that they both stopped short in the doorway, wide gazes fixed on the small sofa between two of the bookcases.

Dean gave them an exasperated look, grimacing slightly as Lucifer nuzzled further into his shoulder. "Er, yeah... He's stoned? Or something?" he offered as an explanation. "And he thinks I'm Michael."

Sam couldn't seem to remember how to speak, merely staring so fixedly it was beginning to get creepy. Castiel, meanwhile, frowned. "How do you mean 'stoned'?"

"I don't know," Dean insisted, waving one hand in the air and pointing vaguely toward the bin. "I dropped a jar of... stuff. And it sort of exploded everywhere. And then he just went kind of loopy."

"Is he sleeping on you?" Sam finally managed to blurt out, gaze never once wavering from his angel who was slumped against Dean's side.

Dean sighed, shifting in slight discomfort. "Yeah... Well, he was just kind of rambling for a while. Then he sort of passed out on me."

Cas, meanwhile, had wandered over to the bin. He plucked out the broken bottom of the jar and sniffed it experimentally, instantly drawing back and frowning as he shook his head. "This is a form of narcotic," he said. "An ancient form. In times past, it was often used to subdue unruly angels and other creatures locked away in Heaven's cells."

"It just made me cough," Dean said.

Castiel shrugged, depositing the jar back in the bin. "It's more hardwired for multidimensional creatures. It wouldn't have much effect on humans or other animals."

"Yeah," Dean muttered. "I just get to deal with a loopy, half-baked archangel. Fantastic."

"He really thought you were Michael?" Sam questioned, finally snapping out of his trance and stepping closer.

Dean sighed. "Yeah. He was just going on and on about..." He paused briefly, voice lowering slightly. "He seemed happy to see me. Michael, I mean. Seemed to really want to make it up."

Sam pursed his lips, gently stroking his hand over Lucifer's shoulder and arm. "He doesn't like fighting with his big brother. I know what that's like."

"Man, this is getting sappy," Dean groaned, but held out his other arm nonetheless.

Sam smiled, quickly moving round and settling himself in the embrace, nestling against Dean's other shoulder.

Dean rolled his eyes, before finally turning to Cas. "I only got two arms," he said.

Cas gave a half-hearted glare. "You know," he said, nodding toward Lucifer. "He likely won't remember any of this. The amount that appears to have been in that jar is rather strong."

Dean shrugged, ignoring Lucifer snuggling closer and mumbling, "Michael" in his sleep.

"Good," Dean said. "Because this is kind of ruining my reputation."

Sure enough, Lucifer didn't seem to remember. At least, he never brought it up if he did.

Dean, once both his arms had gone numb, had managed to manoeuvre himself out from under both his sleeping brother and... whatever the hell Lucifer was. He'd shifted the two of them to lie together on the sofa, where they'd both woken later, and Lucifer had made a valiant attempt to hide his confusion about how he'd ended up in such a situation.

Not long later, the archangel had stomped off to some other area of the bunker and was not seen for the rest of the day, though Sam had soon followed after him.

The next morning, he came downstairs as if nothing had happened.

"Good morning, Dean," was mumbled casually in passing.

Though if Dean wasn't mistaken, there was something not quite as sarcastic about it as before.

A/N: What this is, I just don't know. Whether it makes sense to anyone other than me, I also don't know... Just 'Swan Song', you can just see Lucifer notices how Dean's all "I'm not going to leave you, Sam", and then there's Michael who's just all "I have to fight my brother", and the comparison breaks my heart. And I think, maybe, a part of Dean would find the idea of a big brother abandoning his little brother without a chance doesn't sit right with him.

Lucifer is Sam's other half, he and Dean would be forced to bond eventually!