Welp, it's not a one-shot. Thanks for the interest, guys. No promises as far as update frequency, but there will be more at some point. Merry Christmas!
For the first few hours after Sam carries Dean's empty body to his bed, Cas disappears to parts unknown. Sam's game plan for the moment is to get so drunk he can't see straight. But after the first swig of gin, all he can really do is stare at the bottle sitting on the table in front of him, shivering every few minutes. Suggestions generated by some distant part of his brain flit past him every once in a while—he should sleep, he should hit the books, he should start working on some kind of plan. None of it sounds appealing nor worthwhile. All he's really done is draw warding around Dean's body. If he tries coming back, he won't find an available meatsuit waiting for him. Though that is a small comfort.
He doesn't catch it when Cas first appears but when he suddenly registers the angel's presence he surmises that he couldn't have been here more than a few seconds. The abrupt arrival somehow reminds him of his single short-term goal, and he lifts the bottle of gin to his lips, and grimaces as he swallows. For some reason he assumed Cas would speak before he finished the swig, but silence has settled over the room, so Sam says without taking his eyes off the bottle, the tiredness in his voice obvious, "How the hell are we gonna get him back, Cas?"
His best guess is that Cas has been somewhere in the bunker doing research for all this time. For this reason the long pause after his question is extremely disheartening. Finally, though, Cas responds, "It's a rare occasion when we know exactly how we're going to solve a problem anytime before the moment we do."
A surprised chuckle escapes Sam, quickly cut short by an irrational stab of guilt at his ability to laugh.
"This is more or less unprecedented," says Cas after a moment of silence. "Having a demon flee a living body that didn't have anyone inside it. Do you think there's anything we need to do to preserve the body?"
Sam shudders visibly, but he shrugs. "Your guess is as good as mine. Like you said, we have no frame of reference here. Except Cain. And we haven't exactly got him on speed dial. But I mean… he's still breathing. It. The body." True this is, though so strange. Sam stood at the doorway for several minutes just watching his brother's body breathe regularly, chest rising and falling. It was so easy to convince himself, just for a moment, that Dean was only asleep.
"It's very medically interesting," Cas agrees. "A body does not age while being inhabited by a demon, and though it can sustain fatal injuries the demon can retain control and prevent anatomic shutdown. I suppose there is the question of whether that is voluntary or merely a subconscious process, though I would assume—"
"Cas," Sam deadpans.
Cas snaps his mouth shut, and after a moment of thought opens it again. "I really don't know whether Dean's body will be maintained if we leave it, but I believe I can use my grace to remove all doubt."
Sam raises an eyebrow. "Your grace can be used to do that?"
"There are many things my grace can be used to do. I can think of no reason why this wouldn't be one of them."
"I thought you'd lost your grace?"
The angel grimaces. "I have it back. In some form. It's likely only a temporary fix, but for now we don't have to worry about it."
Sam's silent for a moment, turning it over in his mind. He really can't think of a reason why Dean's body would die and start to rot, since it's already survived the first few hours without mishap. And Cas needs to conserve his energy.
But he would never forgive himself if inaction on his part meant that, somewhere down the road, Dean is unable to become himself again.
He nods, and gestures towards the stairs. "All right. Do it."
They ascend, Sam following shortly behind Cas, and soon stop by Dean's room, which Sam has locked from the inside. He inserts the key into the lock, twists, and pulls the door open.
Cas steps gingerly over the warding in case it's still drying, and for a moment just stands still, staring down at the apparently sleeping form of the man he once pulled from the depths of hell.
Dean was so scared then of what he would become when his year was up and his side of the bargain came due.
His biggest fear has always been, without a doubt, failing in his role as Sam's protector. For the most part, Sam was appropriately grateful for it, but sometimes it just pissed him off. He was an adult and Dean had his own issues to worry about. But coming up in second place was fear of his own future. He has never been able to see himself as the hero he is. He has never had enough faith in his own goodness.
And now, suddenly, everything he's ever wrongfully believed about himself has, completely outside of his control, come true.
Sam rubs roughly at his dry eyes and says, "Just do it, Cas."
Cas obeys, reaching his hand, fingers stretched wide, over Dean's steadily rising chest. He lowers it until his palm is so close Sam might not be sure whether it were touching down against the body if he couldn't see the slight unsteadiness that persists in Cas's arm, and then a soft blue light begins to spread from Dean's heart. It rushes along his extremities, illuminating every blood vessel even through his clothes, to the point that the body looks like some grotesque Halloween decoration. Sam notes, though, that the light stops just an inch or two short of the Mark, weaving around it and creating a significant gap in the illumination of Dean's veins where that godforsaken thing blemishes his skin. For the briefest moment, the body's breathing hitches, and Sam feels his heart stop beating.
Then Cas withdraws his hand, the air begins entering and exiting Dean's lungs normally once again, and the blue light dies. The entire process lasted about five seconds.
Cas turns to Sam, breathing hard. "That will last it a while, at least. You won't have to feed it or give it drink; the grace will sustain it."
"Cas," Sam says, watching the angel with his brows drawn in concern, "you sure you had the juice for that?"
"I'll be fine," he wheezes, and pauses to draw in a slow, deep inhale. When he continues he seems steadier. "I just need rest. This will save you a lot of trouble."
He starts towards the door, and Sam starts to follow, but stops to cast one final glance at his brother's empty body. His gaze lingers on the Mark, and in a fraction of a second he realizes it's eliciting more energy-expending hatred and bitterness than he can afford right now. He looks back towards the door, where Cas is standing, watching him watch the Mark with the same sad gaze he's always had.
"Maybe," Sam ventures, pretty sure their minds are on the same track, "since he's separated from the Mark itself, physically at least, its hold on him will… lose some of its potency."
Cas won't humor him. Not that he really wants him to. He shakes his head without hesitating, and says, "The Mark is what made Dean a demon. Surely it will stay with him for at least as long as he remains that way."
Sam frowns, rubbing the back of his head. "You don't think it'll… like, manifest on the arm of anyone he…" He trails off, unable to complete the thought.
Cas, of course, understands. "Doubtful. The physical mark means nothing, really. I mean, it's extremely significant symbolically, but not as far as how it affects him. It goes far deeper than that—it's something that cleaves to his very soul. He will carry it with him wherever he goes, even if it will no longer be visible."
"Guess it would be too easy if all we had to do was look for poor insane saps with the friggin' Mark of Cain on their arm," Sam mutters.
"Far too easy," Cas agrees. He's silent for a moment. Then, "What is your next move, Sam?"
Sam allows for another pause. He has to. "Honestly? I'm fried. I can't think. The next step is, of course, to find Dean, but that's gonna entail a lot of individual stages that I can't think through right now. My next move is to force myself to get some rest. After that… research. See if there's any way I can…" The pause before the next word is minute, but definite. "…summon him. That's really as far ahead as I can think at the moment."
Cas nods, eyes narrowed in deep contemplation. "And what do you think Dean's next move will be?"
Sam runs a hand down his face. "After finding a body? Getting the Blade back. Though that's gonna be really difficult and he knows it. I guess he'll try to find Crowley, or work on gathering allies, or maybe try to do some research into how to get around the warding or try to set up a trap for me… I don't know. Your guess is as good as mine." He eyes Cas. "What's your next move?"
Cas manages to suppress his weary sigh, but he's extremely obvious about it. "My… comrade very much wants me to come with her to help sort out heaven. Frankly, though, she doesn't truly need my assistance. She wants it more because she believes it will be good for me, with which I disagree. So…" He pauses, and inhales sharply. "I'm not needed elsewhere. I'm going to stay, help any way I can."
Sam stares at the angel, mind going blank, one corner of his mouth curving upwards. "You sure?"
"Absolutely. There is nowhere I would be but here. Why don't you head to your room?" Cas takes the single step to bring him outside the door and gestures down the hall. "I don't have your research experience or aptitude, but I can at least get you a head start."
Some of the weight is gradually shaking its feathers and flying from Sam's shoulders. He won't have to do this alone. A grin flickers across his lips, a real one, the first he's produced in a very long time. "I'm really glad you're here, Cas."
Cas offers a smile back—a little more forced than his own, but still genuine. "Under the circumstances I can't really say I'm 'glad' as well, but I am happy to help. I only hope… I can."
Sam does too, of course he does, but just knowing that he'll have a friend in all this is enough that he thinks he might actually be able to fall asleep. He lets the smile drop from his face after he locks the door and starts down the hallway, but his steps are definitely a little bit lighter.