Summary: It's a split second choice - probably the only one they have left. But Dean makes it, because it's his brother lying there, bound and beaten, with a bomb strapped to his chest counting down all their deaths. How bad could it be, saying yes to an angel? Season 12 AU

A/N: Apparently I didn't have enough to do with The Road So Far (This Time Around). Nope, obviously I needed another story. Damn you, plot-bunnies! Oh well, this one is significantly shorter. Hope you guys enjoy!

Story Warnings: Rated T for some swearing, violence, and dark themes. Takes place somewhere after 12.12 Stuck in the Middle With You.

Chapter Warnings: Angst, bombs, brotherly love, partial character death I suppose?

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Cohabitation

Chapter 1

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Cohabit; v. To exist together.

They stood on either side of the barn doors, weapons gripped in sweaty palms, breaths steady, shoulders taught. Across the length of the door, Sam glanced at his brother, whose game face was securely in place. He was pissed, and rightly so. Sam, on the other hand, was more worried than angry, as was the tendency between the brothers.

Dean caught his eye, and he gave a single, solemn nod.

His brother rounded on the wooden door, slamming it open with a well-aimed kick. Sam followed immediately behind, gun raised over Dean's shoulder to cover him as the two cleared the corners. When no attacker presented themselves, Sam finished a visual sweep of the barn, gun raised to every dark corner, the stalls in the back, long abandoned, and the loft above.

"Cas!" Dean ran forward to the center of the barn where their friend was tied to one of the posts supporting the loft. The angel, beaten and bloody, was propped against the wooden structure, legs spread out in front of him, bound to the post by thick, silver chains stretched across his torso. Dean slid to one knee beside their friend, hands automatically reaching out to wrap around the side of his neck and tap the man gently on the cheek. "Buddy? Cas, come on, can you hear me? It's us!"

"Room's clear," Sam muttered as he tucked his gun into his waistline and dropped beside the two. Dean was still trying to rouse the angel, whose head lolled to the side but was beginning to show signs of consciousness. Sam made to check the rest of their friend over for injuries but drew up short. He threw his hand out, grabbing his brother's arm and halting his movement. "Dean….don't move."

"What? What are you talking-" Dean shot an incredulous glance to his brother, but Sammy wasn't looking at him. He followed the terrifyingly blank expression on Sam's face, focused solely on Castiel's chest. The older Winchester froze immediately as he spotted what he had previously overlooked in favor of making sure their friend wasn't dead. "Whoa."

Welded into the chains by what looked like liquid metal long hardened, was a bomb. It wasn't your Saturday morning cartoon sticks of dynamite or procedural cop show flak vest complete with C4. This looked more like something out of a bad sci-fi show, with four glass cylinders filled with glowing, ethereal blue liquid, connected to a digital readout flashing numbers in clear, deadly white LED.

06:14…06:13…06:12…

"Okay….Okay." Dean stepped back from Castiel slowly, releasing the angel's neck and tearing off his jacket. "We gotta get him out of there. Any ideas?"

Sam very carefully leaned in to examine the device. He didn't dare touch any of the connecting tubes or wires, some of which were definitely not of human design or technology. There was no removing the bomb from the chains. It looked to be permanently welded in place, added after Castiel had been bound by the heavy chains. Sam grimaced at the thought, realizing that the material of chain was melted in some places, warped into the mechanism. It honestly looked like someone had poured liquid silver on top of the angel and stuck a bomb in the middle of the mess.

He prayed Cas hadn't been conscious through it.

05:46…05:45…05:44…

Slowly and with every precaution he could, he reached between two rings of chain and pulled at Castiel's trench coat. The younger Winchester sucked in a breath when his worst fears were confirmed by the lack of give. The smelted metal had been applied atop the angel, seeping into his clothes and skin and solidifying into place, sealing the two together.

They weren't getting Castiel away from that bomb. Not in one piece.

"Dean-"

"Can you make it stop?" Dean interrupted him, knowing full well what he was about to say. He could see it in Sam's eyes: those pained, puppy dog, soul-brown eyes that looked his way in absolute terror. Even if he hadn't seen the evidence for himself, Dean knew what Sam was thinking. "Turn it off, or something?"

"I don't even know what it is," Sam countered, rocking back on his heels to stare at the device. He'd never seen anything like it, and he had just as good a chance of blowing the three of them up five minutes sooner than he did at stopping it.

"D'n, S'm."

"Hey, hey, buddy, you with us?" Dean leaned back in, cupping Cas's neck once more as the angel opened weary, pain-ridden blue eyes. "That's it. Morning sunshine."

"It isn' mr'ng." Cas stared up at them with squinted eyes, blinking through the blood dripping over one eye and the other already swelling up from what would be a hell of a black eye. He tried to sit up, only to grunt and gasp at the abrupt reminder of his injuries and the lack of mobility presented in the crushing, pinching chains wrapped around him. "Wh't h'ppn'd? Wh'r are we?"

"You got nabbed by those douche-nozzles," Dean bit back, jaw clenched and words bitter with anger and the need for revenge. "But we're here now, and we're gonna get you out."

"Out?" Castiel's head lolled to the side before his chin found respite against his chest and he stared down at the ticking numbers reading out across his torso. It took him a moment to parse their meaning, to remember the beating he had taken at the hands of the British Men of Letters. Being thrown against the post and bound in the abandoned barn, the hot smelt of liquid metal pouring over his vessel and the excruciating pain that followed.

His eyes widened as he stared down at the bomb, ticking away on his torso.

05:01…04:59…04:58…

"You ha'f to get out," he mumbled against his chest, lifting his head to look at the two brothers – his brothers – with terror-filled eyes. He repeated himself, louder and with more effort and urgency, "You need to leave. Now!"

"We're not leaving you, Cas," Sam answered immediately, still staring at the mechanism. He was fairly certain which of the wires was the lead, and had identified one false lead so far, or what he was pretty sure was a false lead. But real bombs weren't like the movies. It wasn't a simple 'cut this wire and the clock stops' and, to be honest, Sam wasn't an expert. Bomb disarmament wasn't exactly in their daily routine.

"Call Garth," he instructed his brother, standing up to pull his own jacket off, already sweating in the Louisiana night-time heat.

"Garth?" Dean sounded less than confident in his brother's choice of bomb expert, but he already had the phone pressed to his ear, ringing.

"He, uh, told me he used to keep a flak jacket in his armory." Sam huffed out a small laugh as he knelt back down carefully beside the angel. "He may know how to disarm one."

"Yeah, don't think this is your standard flak setup, Sammy," Dean mumbled even as he started pacing. "Pick up, pick up. Come on! No answer."

"Try again," Sam demanded, even though his brother was already doing just that.

04:17….04:16….04:15…

"Sam, l'sten to me." Cas's pleading blue gaze locked on his and Sam raised his eyes from the device to his best friend. "It's n-not explosive. I's grace."

Beside them, Dean froze in his frantic movements, dropping the phone to his side. "What?"

"Cas, what do you mean, it's grace?"

The angel glanced down at the bomb strapped to his chest before looking between the brothers. "An angel's grace. They said they had it…for a while. M-mixed with holy oil and a ch-chemical I didn't…."

Sam glanced down at the ethereal blue liquid flowing between the containers. The chemical was probably nitroglycerin, given the viscosity of the material and the lack of additional coloring. Putting the three together with an incendiary…. The near college-graduate and brains of the team rocked back as he realized what Cas was trying to say. He looked up at Dean, who stared at him with a clear 'what?' expression.

"The blast could take out a city block," Sam whispered, almost numb. "Dean, this thing is going to clear a…a three hundred foot radius, at a minimum."

"What are you saying, Sammy?"

"You have to get clear." Cas stared up at Dean, the desperate plea in his eyes was almost the hunter's undoing. "You need to run."

"We're not leaving you." The hunter moved behind the angel, away from those pained blue eyes and started tugging on the chains behind him. He couldn't even find where they ended. There was no lock, no tether. The chains appeared endless, which made no friggin' sense.

"Dean, if we don't leave now, we won't get clear of the blast," Sam said quietly, though he didn't make any move towards standing up either.

"Then figure out a way to stop it, Sam! We're not leaving." Dean gave the chains an experimental tug, but they barely budged and Cas only groaned in response. He stood back, telling Cas not to move, and trained his gun on one of the chains. The ricochet was loud, but thankfully non-damaging. Some of the post chipped away, raining bits of splinter down on them. Unfortunately, the heavy link had little more than a chink in the metal to show for the effort and noise.

"Will you just listen to me?" Cas struggled to turn his head, to look at the hunter behind him and then the one in front, carefully pulling apart the various wires and tubing. "You need to leave. I need you both to leave. Please!"

Sam didn't bother answering, focusing solely on identifying which wires he would need to cut, splice together, and disconnect. Dean, however, rounded back on the angel, kneeling in front of him with a firm hand gripping his shoulder tight.

"You listen to me, you son of a bitch. You're family. You don't leave that behind."

Cas grit his teeth and let out a groan. His gaze grew more livid than desperate. "So three will die instead of one?"

Anger, Dean could deal with. He was good at anger. "If that's what it takes."

The angel let out something between a keen and a snarl, staring at the two humans who had made him what he was, who meant more than the world to him, who were going to remain the stubborn idiots he'd first fallen for, and would now die beside.

03:36…03:35….03:34…

"Okay, Dean, I think I got it." Sam leaned back on his calves, pulling his pocket knife out and flipping it open. He gave his brother a harried look. But Dean only nodded solemnly back, complete faith in his younger sibling. "Here goes."

The three Winchesters collectively held their breaths as Sam cautiously slipped his knife under the first wire. Nitroglycerin was infamous for its instability, particularly to physical shock. The fact it hadn't set off with Dean's haphazard shooting was a miracle. Sam didn't even want to test what a minor bump to the device might do when mixed with a volatile substance like grace.

To be honest, they were lucky the grace hadn't ignited the chemical on its own already.

He put as much pressure as he dared against the blade, gritting his teeth when it refused to cut through the wire. With a frown and confusion filtering across his brow, Sam repositioned the knife and tried again. Nothing. The plastic protection around the wire didn't even dent.

03:03….03:02….03:01…

Sam sent his brother a worried look, then tossed caution to the wind and started a steady rhythm of sawing motions with the blade. Still, nothing.

"Try mine." Dean held out his bowie, which was impractical for a delicate operation like this one, but Sam didn't really care at that moment. He swiped the knife from his brother and pulled at the wire with more strength then ever should have been needed.

The length of wire strained against the edge of the blade, but held firm.

"Oh, what the hell!" Sam fell back with a shaky breath, staring at the undamaged device, steadily ticking towards their death. He grabbed at the plastic shealth, rubbing it between his fingers. Runes lit for just a moment, reading out along the wires that fed back into the device before they faded. A protection spell. He looked back at his brother, seeing the same wide-eyed, 'we're screwed' expression written over his face.

Dean swallowed, looking back down at Castiel. They didn't know what else to try. With a furious growl, he launched himself back to his feet and threw his phone back up to his ear, once more dialing Garth, not that him answering would do them much good now.

Sam met Castiel's gaze, and didn't know what to say. "Cas…"

"You can still get out, Sam," the angel breathed, imploring the two men to leave. "Please. You can still make it."

The young hunter seriously doubted that, given the several hundred feet they would need to run in less than three minutes now. And his estimate was likely a gross under-calculation, given the ingredients and amount of them sitting on Cas's chest. Not that they'd ever leave the angel behind, so it was a moot point either way.

"Still no friggin' answer!" Dean chucked his phone across the barn, watching it shatter against the old wooden walls. He dropped beside his brother and his best friend, panting in anger and fear. "Cas…"

"It's okay, Dean."

"No, it's not! I'm gonna kill those bastards."

Cas gave him an almost pitying look that Dean could read as more, as sorrow and acceptance and love, only through years of knowing the angel. He didn't want to see it though, didn't want to acknowledge what their failure meant in those blue eyes.

02:12….02:11….02:10…

Sam went back to pulling at the wires, sawing at them with the blades, but whatever magic had built the device and bound it to Castiel's chest also protected it from tampering. He even got to the point of jostling the thing enough to know the spell work was keeping the nitroglycerin stable from exterior stressors as well. This bomb wasn't going off until it was meant to – which was likely an exact calculation on those measured bastard's behalf, knowing when Sam and Dean would show to save their friend.

Dean cupped the angel's neck again, holding onto him with both hands as he stared into his best friend's eyes. "We're not leaving you, Cas."

The angel let out a broken sob, a couple tears slipping free of his lashes as he looked up and away before meeting Dean's steadfast gaze. He nodded, though it looked like it cost him the world to do so.

Sam glanced at the two, catching his brother's gaze. He saw the end there. But, despite walking into this with every hope that they would find Cas alive and bring him home…there were worse ways to go. He gave a small nod to his brother, whose return gesture said the same without words.

01:46…01:45…01:44…

"Cas." The silence that had filled the barn for what was only seconds, but felt like minutes, was broken by Dean's voice. Blue eyes looked up once more to lock on the hunter, who was staring at him with a mix of emotions he did not immediately understand. "Is this thing tied to your grace?"

"What?" He squinted at the human before him, not understanding the question or the purpose behind it.

"Your grace, is it intact or is it attached to the bomb somehow?"

Sam lifted his head at the thread of desperation in his brother's voice, the vestiges of a crazy plan that had sparked hope in those green eyes. The younger of the two didn't know what it was Dean was getting at, but he'd take any Hail Mary his brother was able to pull out of thin air right about now.

01:31…01:30…01:29…

"No," Cas mumbled, eyes darting back and forth as he sought within himself for the state of his battered grace. "It's intact."

"Okay. Okay." Dean nodded absently, almost to himself. He cupped either side of Cas's face, bringing those eyes back up to meet his. "Then I'm giving you my permission."

Cas frowned, eyes squinting tight in confusion and pain as he was unable to parse what Dean was talking about.

"Cas, I'm saying yes."

Sam stiffened beside them, staring at his brother with eyes wide from both shock, worry, and the first inclination of hope. "Dean-"

"Cas, come on, man, it's the only way."

The angel's unearthly blue eyes widened as he finally realized what the human in front of him was suggesting – was offering. "No. No, Dean, I won't do that to you-"

"I'm not asking," the hunter barked back, thumbs tapping the sides of Castiel's face. "We're running out of time! You climb your ass on in here until we can find you another vessel."

01:19…01:18…01:17…

But Cas was shaking his head, for all the pain it caused him. "You don't understand. I'm u-used up. I won't…I won't have the strength to leave, not for a while. M-Maybe not ever, Dean."

The hunter clenched his jaw, but the resolution in his eyes never wavered. "You hear me backing out? I'm still saying yes."

"No, Dean…." Cas's voice broke midway as the shattered angel continued to deny him with all the strength he had left.

"Damn it, Cas! Look at me." Dean waited until blue eyes locked on his own, however miserable and pained they were. "You're my brother, man, and I'm not losing you. If that means you riding shotgun for the rest of our lives, so be it. It's better than dying."

He could see the moment he broke through, the moment resolve faltered in the angel's gaze, and he grasped hold of it, tightening his hands against Cas's face. "Come on, Cas. Get your feathery ass over here, already. You got my permission."

Castiel closed his eyes tightly, tears forced past thick lashes to slide down his cheeks. He rested his head against the post behind him and for a moment Dean was sure he was obstinately refusing to save his own life, and possibly theirs too. But then light began to build beneath his skin, filling his throat. The angel keened, voice breaking with a sob before the blinding light took over and he threw his head back against the post, mouth and eyes wide with the white beam.

Sam took a hasty step back as he watched that light engulf his brother, flying through every orifice of his face. It caused his body to go rigid, arms thrown wide and head tilted back as Castiel's grace engulfed him. And then it was over. The barn seemed terrifyingly dark in the absence of that pure light. Dean knelt on the floor, doubled over and braced by locked elbows as he breathed heavily through his nose.

00:42…00:41…00:40...

"Dean?" Sam scrambled back over to his brother, glancing at the ticking bomb attached to a now lifeless vessel. "Cas?"

His brother groaned, curling his fingers against the straw and dirt of the barn floor. When his eyes shot open, they were pure green. "It's me. It's me, Sammy."

"And Cas?" The younger hunter couldn't help but glance at the limp body slumped against the post in front of them.

"He's in here," Dean confirmed. "I got him."

Sam barely let the words finish forming before he was hauling his surprised brother to his feet and all but dragging him as fast as he could out of the barn. Dean, unprepared for the sudden movement, stumbled along beside him as Sammy ran as fast as he could straight for the Impala, pulling him along behind.

The younger Winchester threw open the passenger door, shoving Dean in and rounding the car as quickly as he could. They weren't going to make it. There was no way they would clear the blast radius, no matter how fast he drove. Still, he threw himself into the driver's seat, catching Dean's hastily – and badly – thrown keys, jamming the square one into the ignition and lighting the engine up as fast as he could in rapid succession.

Dean caught a single glimpse through the still open barn doors of Cas's unconscious body, chained to the post of the loft, time steadily ticking down in neon white numbers. Then Sammy threw the car into gear and gunned it down the dirt drive that had led them to the barn and their friend. He glanced in the rear view mirror at the rapidly shrinking barn behind them, mentally counting down the time they had left. They weren't going fast enough.

"We aren't going to make it," he whispered, fear coloring the last of his words.

Beside him, Dean suddenly stiffened, back straightening and eyes lighting up blue.

Sam glanced at him, then the road, then him again, trying to keep the Impala on course at dangerous speeds. "Cas?"

Dean's head turned stiffly towards him, in a way very alien for his brother. Glowing blue eyes took him in for only a second before a hand shot out, curling over his forehead and coating the world in darkness.

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A/N: Next chapter should be up in a week. Hope you enjoyed! Please review and let me know your thoughts!