Notes:

So, this story has been swirling in this brain of mine for quite some time now and I've been putting out fliers O_O for anyone to adopt the bunny, but no one seems interested so I'm going to try my hand at this. Hardly a writer, (duh lol) but I know a thing or two about the basics (Parksborn fic is still in progress), so hopefully this doesn't end up as a totally "bad fic" from what others so like to call plots not to their liking.

This is AU from Season 1's Season Finale: Devil's Trap and Season 10's Episode 3: Soul Survivor.

Chapter One

Sam's looked up on all kinds of lore on demons, of Cain and Abel, what little he can find on them, the Mark. He's read the Bible cover to cover with a big fat nothing for his trouble, has scoured through entries in witchcraft books for tracking spells. Sam hasn't left a phrase unread, a single page unturned, went as far as torturing, killing humans and demons alike for any scrap of information that might bring him closer to his brother.

Since Dean's escape from when he left him tied down in the dungeon where he's supposed to stay put, Sam's gone from bad to worse. He knows this, is aware how much he's crossed the line from what makes him human a few months past. He's no different now from the things they hunt in his desperation to get his brother back. Maybe he is a monster. Maybe he's worse than the demons, hell, worse than the very same one he's trying to save. He had no qualms sacrificing an innocent man's life or the ones after that. It should bother him. The old Sam probably would.

Funny thing is stuff such as humanity and good old conscience matters very little to him these days.

It almost feels like being soulless again.

Dean's been leaving dead bodies in his wake. So much for giving Crowley the First Blade to throw somewhere preferably at the bottom of a volcano thinking it's a foolproof plan in separating his brother from the damned thing. Dean has been the exact opposite of thrilled finding out Crowley sold him out. Sam can only imagine what went down between them when Crowley can't even hold on to one stupid blade.

Now if only his brother had enough sense to actually ice the irritating son of a bitch.

Dean's given in to the call of the Mark that much is obvious. Sam's seen the corpses, the fatal wounds causing the deaths, a whole lot of jagged edges like teeth reminiscent of the First Blade. Dean's sloppy. Too much blood and gore, like he's trying to prove a point, or maybe he's burning out whatever humanity Sam stabbed into him from the injections. Try as Sam might, to his frustration, even with all the foreknowledge in his arsenal, he can't pin his brother down. Dean's a demon for several months now. It won't surprise Sam that Dean's learned to travel via Black Smoke Express, possessing unsuspecting victims, keeping an eye out on Sam, making sure he's always ten steps ahead.

Half a year passes without any solid lead on Dean. Oh, he's heard through the grapevine about Crowley's uncontrollable "pet", but dialing up the King of Hell proved to be unproductive, and Sam doesn't have the patience to deal with a demon acting like a jilted lover.

"Squirrel's hiding Moose, he doesn't want to be found. But feel free to get back to me if you do find him. He's bad for business and my peace of mind. Tell you what, I'll even help you tie him down this time. The sooner he becomes human, the better for all parties involved."

Sam's ever curious brain wonders if his blood's still running in Crowley's meat suit. The demon's always been a pain in the ass, but his fascination with Dean, how invested he became ever since the trials after getting pumped full of Sam's blood, even now, sounding like a wounded pup when his brother's name is mentioned. Crowley's feelings on the matter of his brother almost seems like it came from Sam.

Yeah, not dwelling on that.

Hannah, Cas' sister or girlfriend, hasn't stopped sending Sam these disapproving looks in regards to his poor life choices since the day they met. Sam likes to think it's merely something to do with his recent actions, no matter how unsettling that sounds, but he knows deeply rooted judging eyes when he sees one. Looks like being Lucifer's vessel will always and forever alienate him to the rest of Cas' family. Even Gadreel rode shotgun at one point, the same archangel that let the devil in at the Garden of Eden, the one that killed Kevin and— long story short, Sam's angel associations happen to always be with the biggest bag of dicks. Doesn't matter. Sam's not asking for her approval anyway.

Castiel on the other hand has gained the title of resident den mother.

"Sam. You need to eat. I can no longer stand idle by while you slowly kill yourself through neglect."

Speak of the devil. Or angel, if one wants to be specific.

Sam's reply is a simple pursing of lips, a slight head tilt. He's acknowledging the fact that not bothering to eat unless his body's practically screaming for it may not be one of his better ideas, but he has no time for something as trivial as food.

"Not now Cas." Sam says, ninety percent of his concentration fixed on the Sumerian book he's currently immersed in. He can't afford to get distracted. He's been going over these three pages worth of spell casting for weeks. Sam's beginning to think this might actually work, the answer to at least one of his problems. "And you're one to talk. Your body's giving out on you. Again."

"I will not be stealing any grace." Cas replies, chagrined. "Not at the cost of a brother or sister's life."

"You'll die." Sam shoots back matter of fact, cocks his head minutely to see the angel's worn out, tired face. Sam can empathize, one of the perks of actually having a soul despite feeling relatively numb and indifferent to everything else that doesn't concern Dean. If there is one thing he hated about being soulless was his complete disregard of his brother. He doesn't ever want to be that kind of unfeeling bastard again.

Sam can't imagine killing Dean, even if it's for his own good, or the greater good. He's going to find a way. There is always plan C to Plan Z and if that isn't enough, he'll come up with something else. Bottom line is he's not giving up on Dean. Period.

Cas has multiple siblings out there, some he's only met in passing before the Fall no doubt. What he feels for his brothers or sisters can't hold a candle to what Sam had gone through in his lifetime after losing his brother and thinking he's lost him for good. The hell hounds, the too many Tuesdays, six months of his personal Hell afterwards, the thousand years in the Pit, Purgatory, Metatron. Cas' relationship with his siblings is nowhere near what Sam and Dean share. He can go do the smart thing and steal grace from one that's out for his blood.

"I will deal with it when the time comes." Cas answers stubbornly just as Hannah comes into view, stone-faced as ever as her gaze sweeps over to Sam then to Castiel. Sam barely holds back a snort at the blatant adoration in her eyes. Sam might feel generous one of these days and lock them in an angel proofed room until they sort out their big explosive incestuous feelings. Hey, that totally worked for him and Dean.

Sam runs a hand across his face, sighs.

Oh, he made himself sad again.

"Castiel. A word?" Hannah says, one quick look at Sam, a slender hand resting along Castiel's arm.

Sam makes a shooing motion when Castiel remains to look at him with soulful, pleading, puppy eyes. Sam swears the angel's learned it from watching him. "I will bring sustenance later in the day. I'd appreciate if you would eat even just a small portion from it, Sam."

Sam probably gives a nod of ascent but he's not quite certain, not when he's still elbows deep in Sumerian Literature.

Sam's studiously scribbling notes and symbols down on a legal pad of paper when Hannah's suddenly storming into the library, too weak herself from the Fall and prolonged stay on Earth to do their fancy Angel Airline thing, pale, frantic and begging him to save Castiel.

He stands there uncomprehending until Hannah clears up what she's asking of him. And then it clicks. Hannah acts a lot like how Castiel had been during their first months together, all good little soldier and a stickler for following orders; it registers to Sam too late that she must be just as unwilling, probably even more so in taking a brother or sister's grace with her bare hands even if it means saving Castiel's life.

It falls on Sam to hunt down an angel, contain its grace in a vial and force feed it to Castiel.

Of course, this is his life now. Demon brother still MIA, reluctant host to a deteriorating, stubborn headed angel, while also dealing with his jealous, bipolar-ish sister slash girlfriend. Sam needs an Advil, or ten.

Castiel's impending death inevitably cause Sam and Hannah's relationship, barely tolerating each other at best turn to conspiring together in a day's time.

"You realize going after an angel's going to paint a pretty big target on my back, right?" Sam points out his eyes challenging as Hannah paces in front of him. Castiel's his friend and he understands more than anyone the desperation to save the most important person in one's life, Dean Exhibit-fucking-A, but he's not about to lift a finger unless Hannah's going to make it worth his while.

She's been keeping her distance all this time, like Sam's something she's afraid of catching, like a virus or a contagious disease. Now Sam's gotten over any kind of hurt feelings to what angels think of him, but it still ticks him off whenever someone judges him just because he's Lucifer's vessel. Like it's a free pass to being a dick. Or a grade-A bitch.

Sam's been busy tracking Dean's whereabouts and he's not about to accept a request that would most probably have him end up at the wrong side of an angel blade. Without a concrete means of protection, something to ensure Sam's not going to get every available winged bastard after him once he offs a specific target, he's not going anywhere.

It can be argued that he might be slightly suicidal when it comes to bringing Dean back in the sense that he doesn't care much what happens to him afterwards as long as Dean's cured. But that's just it. He's willing to do just about anything for his brother. Castiel? Not so much.

Eventually, Hannah relents and reluctantly acknowledges that Sam is no good to her dead. Woman knows her priorities, Sam can respect that. It's not even a question. He will die if he goes out unprepared and unprotected. Cole's another matter that he tries not to think about.

"I have something I can give you. It will cost me greatly. My grace…" Hannah starts but then trails off as if pained only to shake her head, face steeling back to its stone-cold soberness. "It will help your chances for success. I will help you Sam. I will do what I can. All I ask is your promise that you will not fail. That you will try to the best of your abilities of bringing that grace to Castiel.

Hannah's fingers are kind of digging pretty hard on his bad arm Sam could barely resist a wince.

"Yeah, okay." Sam answers jerkily as he tries to shake Hannah off. The angel seem to realize then that she's got her hands all over Sam and recoils. She abruptly pulls back as if burned, as if she's just touched something absolutely revolting. Sam sighs, resigned.

"Apologies." Hannah tries but it falls flat. She doesn't sound apologetic at all. Sam lets it go.

What Hannah deems neccessary to give Sam basically has to do with carving Enochian symbols into his soul which as it turns out is a bitch to sit through and almost hurts as much as being the sole recipient of Lucifer's wrath. Sam's never been more relieved once Hannah's got her arm pulled back and away. Once the spasms and pain begin to subside, Sam soon finds out she's given him the equivalent of angelic X-Ray vision as soon as he opens his eyes. It allows him to see past the vessel and into the grace inside, a metaphorical switch he is able to turn on and off at will without getting his eyes burned out, which Sam finds, he really appreciates.

On that note, Hannah's grace is beautiful. Radiant. It shines pure white light it practically steals his breath away. However, one glance at Castiel's stolen grace and Sam's never screwed his eyes shut so tight so fast. Sam's never looking again unless Castiel's rightful grace is back for good. That thing currently residing in him is a stuff of one's worst nightmares. And he's seen some pretty messed up crap.

Later in the day, Hannah makes compelling points of how Sam needs to be cloaked beforehand. It is going to be no use if he can tell which humans has angels riding shotgun when he's just as recognizable. He has to give it to her. She's damn efficient if nothing else. Sam appreciates the thought, though he knows that it has nothing to do with his safety, but the success of the mission.

If his first attempt at stealing grace fails and it circulates that Sam's trying to kill angels for whatever reason, it's going to be very difficult for him to move forward with any further attempts and Hannah won't risk it for Castiel's sake. Case in point, Sam Winchester's a very recognizable face to angelic folk, his soul like a beacon broadcasting Lucifer partied and went to town in there that it's near impossible to hide his true identity.

Keyword, near impossible. And with an angel quite high up in the command chain to back him up, Sam's assured Hannah won't mess it up.

While Sam continues to find a way to track Dean, Hannah busies herself with preparing him things he'll need to ensure his safety. She makes hex bags to hide him from anything supernatural, demon and angel alike. Sam knows how to prepare one himself but Hannah seems more than content to do something with her hands. Next comes the hard part. As if carving into his mangled, flayed soul isn't enough she metaphorically throws some kind of supernatural blanket over it to make him undetectable as Sam Winchester. She then paints complicated sigils and wards into his skin and under meant to waylaid perception, a disguise of sorts in cases of physical encounters. Awkward bonding moment if there ever was one. Sam's never felt more uncomfortable around a woman while naked.

Sam's anti-possession tattoo makes a comeback as well on a safer place, less chances of it getting burnt out.

And then he realizes just exactly to what extent Hannah's sigils and wards are capable of.

Sam regrets ever giving her the go signal to go crazy on him.

The younger Winchester feels the exact moment the change register, the full reality practically punching him in the face. He topples over and free falls onto the floor because his whole goddamn center of gravity's suddenly shot to hell, his clothes practically dragging him down.

Hannah's turned him into a girl, the younger Winchester realizes dumbfounded. And it's not metaphorically.

It's been exactly twenty years since the last time Sam's dreaded looking into a mirror.

The angel's chosen form for Sam appears as a blonde haired teenage girl who doesn't look any older than fifteen. The girl looking back at him from the mirror has the same shade as his brother's eyes, the freckles dotting the bridge of Sam's nose similar to that of Dean's in his pubescent years. And Jesus Christ. Those lips are also Dean's, or at least nearly alike Dean's. Sam pokes both forefingers at the corners of his- her? mouth stretching it to a smile and notices his left cheek is at least still dimpling. Something that's solely a character trait of his.

Sam realizes with a jolt that the girl looking back at him kind of looks like mom.

Sam feels the strongest urge to throw a fit and scream and kick whatever he can within reach. His current appearance is like a combination of Mom and Dean and a little bit of Sam and Dad thrown in. He's certain that Hannah's either developed a sense of humor or decided to torture him on the side.

If Mom didn't die and their lives didn't get fucked to all high hell, he can imagine this kid would be how their little sister would look like.

The thought only further caused his depression to spiral and Sam spent the next days, hours, every waking second raging at Hannah for making the change without running it by him first.

But the infuriating thing about Hannah is she's matter of fact. She honestly doesn't understand or see why Sam would have an issue with a female body, especially as young as this one is when he is to use it for his mission. Humans and even some angels, she points out tend to underestimate females as the weaker gender, especially the young ones, and are often blindsided by this false sense of security.

"You wanted to find your brother. Would this not be a more effective approach in the case that you do get close enough? Same as the rogue angel, Dean will not be expecting this little girl to be a trained hunter, Sam Winchester, won't you agree?" Hannah says, looking at Sam like he's four. Sam eventually relents, accepting the logic as sound and doesn't waste precious time dallying about.

Sam's forced back to rigorous training, to adjusting to his new body as fast as humanely possible. He takes comfort in the fact that Hannah's assured it is not permanent. It's surely not the first time he's been cursed into the opposite sex, one such situation was when Dean managed to piss off a witch at one of their hunts in Idaho and Sam had been in cursing range. He'd been stuck in that form for nearly three weeks.

He might not like it, but it's proven to be effective so Sam took it in stride. His mission to find a substitute angel's grace to replenish Castiel's own went without a hitch. It was almost too easy if he was to be perfectly honest. Sam later on agrees the disguise can stay until he finds his brother and gets him treated. Sam's decided to steel himself for a lifetime of girl jokes once his brother's no longer black eyed.

The least Castiel could have done once he's back on his feet, newly acquired angel grace pumping through his veins is give Sam a deserved thank you. But what he does instead is lock himself in his room like a sulking teenager after outright staring at Sam's new appearance far longer that what he's comfortable with. Predictably, Hannah follows him in his man-angsting over a sibling's loss of life leaving Sam with his own share of grief.

Things went back to normal after that, or at least what counted as normal for Sam.

He resumes reading up on everything he could get his hands on. A good amount of the books he's hoarded involves a healthy amount of tracking spells. Nothing has worked so far however. Or maybe they did work but his brother in demon form probably has the ability to sense what Sam's attempting and is getting out of dodge at the first possible opportunity.

Summoning Dean as a demon using the usual means, like what they do with Crowley ain't doing crap either.

The only one that seems to at least have a fighting chance is a blood-calling spell. Something that would force Dean to Sam's doorstep using the link between them as soulmates, brothers, lovers, blood. But the spell would take a lot out of Sam as some penance or sacrifice and pretty much render him useless after completion which— not good.

If it works and Dean appears, he's as good as dead. If it doesn't, he'd end up month after month searching for another solution. Time that he does not have if he is to have any chance of saving his brother. Now, Grandpa Henry's type of blood-spell might work, but Sam can't risk ending up who knows how many years in the future and getting stuck. There's always feeding on demon blood to power himself up and go head to head with Dean, but Sam doesn't trust himself to have any a sense of self left once he's managed to get hopped up on that addiction.

A few more weeks pass. Sam's by then seriously reduced to considering the demon blood option in his desperation when it hits him. And it hits him hard. Like a punch to the solar plexus, the epiphany rendering him frozen in shock.

Castiel had been human once. But he'd taken another angel's grace to elevate himself to winged status however temporarily. It dawns on Sam like a first breath from being underwater too long that he was, still is the true vessel of an archangel. If there is anyone who could withstand forcefully sucking in angel's grace to a human body, it'd be him. He is meant for it, heck, designed for it. How could he have missed that?

The answer's been staring him in the face all along. If it goes according to what Sam hopes it will, he'd have to take in grace strong enough to aid him in capturing, technically, the first demon ever created. Cain is a problem for another day. Dean won't have a chance of escaping again. Sam won't let him. Sam will be prepared; will keep close watch over, never take eyes off his brother until he's done with his treatments.

It makes perfect sense.

He sees Dean's proud big brother smile, complimenting him, 'damn right my baby brother is a genius' as he makes fun of his enormous brain. Dean tries to give him a noogie and fails, like always, and Sam's laughing his ass off, calling Dean a midget. They're thrashing and kicking on the floor, trying to one-man up each other, acting like the twelve and eight year olds that they really are. Dean cheats and wins over the playful scuffle by pinning Sam to the floor, straddling his waist, eyes bright and breathtaking smile in full view before leaning down and kissing him.

"I won, bitch."

The kiss is chaste, light. Dean's clearly teasing him by holding back. Sam huffs, laughs and pulls him closer instead.

"C'mere, jerk."

It's only when he sees a blurry figure by the library's entrance that Sam blinks back to the present, realizing tears are running down his face. He hastily wipes them away, finally seeing Castiel clearly. With a tight, pained smile, Sam says some lame excuse about something and leaves.

He doesn't want to be around Cas in these moments of weakness, has always hated seeing the pity in his friend's eyes.

An hour later and Sam's already obsessing over angelic literature like a mutt with it's new chew toy.

Sam knows that there's always the chance that gulping down angel grace might kill him instead. He remembers Anna's grace finally returning home, how she had been blasted away to god knew where. Recalls the exploding humans volunteering to be vessels that couldn't withstand the sheer power of an angel's grace during Bartholomew's failed attempt at ruling over humanity after the Fall.

Sam should be thinking over these very valid points, but can't bring himself to care. Because. Not important.

Dean is.

And frankly, Sam's at the end of his rope. If there's even the smallest chance of this working, he'd grab it with both hands, not sparing a thought of what it might do to him. As long as he finds Dean, cure his brother, that's all that matters.

Sam of course would like to stay alive afterwards, granted he doesn't go nuclear upon angelic grace consumption, long enough to chew his brother out for being the biggest dumbass jerk in the planet for taking on the Mark to himself without thinking of the consequences.

Sam knows what a hypocrite he is. With what he's hoping to carry out, he's no different from Dean at all.

He'd been righteously pissed at his brother at first for making the deal with an angel in order to save his life. But in all honesty it all really stems down to the fact that he's had enough of Dean and the deals he's always so eager to make to protect Sam, because it always more or less ends up in Dean compromised or worse and ultimately leaving Sam alone. And no, he can't live like that again.

He'd been driving to a cliff when he hit that dog before meeting Amelia. He bolted. He'd been that close to giving up.

What he said to Dean, about what if their roles were reversed and it was Dean dying and the only way to help him was to go behind his back, keep secrets, letting the fear of losing his brother rule over him, how he'd give Dean the courtesy to make the decision for himself. Consumed with the feelings of betrayal and anger that he'd been, Sam realizes only belatedly how untrue it is. It's the same situation and there's no way Sams's going to do the 'right' thing of 'respecting' Dean's wishes. Especially since his brother's a demon and doesn't know any better.

And really, since when did Sam ever manage to keep a straight head when his brother's welfare, his life was on the line?

After the commitment they made to each other inside that church during the final trial, after he'd thrown Gadreel out and Dean later asking for forgiveness to which Sam gave it without preamble, after the promise they made of a new start, Dean's going to be so pissed if Sam manages to kill himself while he's black-eyed. Then turn that anger and hatred inward for failing Sam. Growing and festering.

Sam really hopes to hell, (bad choice of words) that he doesn't end up dead after this whole ordeal is over.

They were just beginning to be brothers and lovers again.

Days later, with papers upon papers of his research notes crammed into the pages of his journal and a bag full of supplies slung over one shoulder, Sam leaves Hannah and Castiel inside the bunker and ventures to find himself an angel to gank.

Hopefully, Hannah won't mind too much Sam borrowing her angel blade.

A/N: Like it? Hate it? Would love to hear your thoughts. I would greatly appreciate it. Thank you! Comments are food for the soul :)