A/N: This is not the kind of fic I typically write, both in setting and angst. But the idea wouldn't leave me alone, so here it is. No Slash! Just platonic Sam and Cas. I thought they had some really sweet bonding moments in Season 9. ONE-SHOT

"One Piece at a Time"

They'd been tracking Dean for three weeks straight, following a series of bar fights and knocked over liquor stores. Dean's recently acquired demon nature seemed to enjoy playing Bonnie and Clyde with his new pal, Crowley. But at last the demonic duo had worked their way back to Lebanon, giving Sam and Cas hope that a small part of Dean might still be reachable, might be trying to come home.

They were wrong.

The warehouse they expected to find Dean taking up temporary residence in had a dozen demons waiting for them. One with curly black hair stepped forward, a sneer curling his lip.

"The King of Hell sends his regards."

Castiel could feel waves of wrath wafting off Sam as he raised Ruby's knife. Whether Dean had a say in this ambush or was completely ignorant of it made no difference. The older Winchester had not come back to the area for them.

Castiel drew his angel blade as the demons charged. He and Sam were sorely outnumbered, no matter their skill. Sam was just a man, albeit a strong fighter, who took down two demons before he was overwhelmed by three more. They pinned him against the wall, one wrapping meaty hands around his throat and squeezing.

Castiel thrust his blade into a demon's chest and wrenched it back out before the orange lightning had a chance to fully spritz throughout the demon's body. Slashing in a wide arc, he sliced through another's throat and across a third's chest, carving bright glowing fissures through flesh. Crimson sprayed the air. But there were too many.

Sam was twenty feet away, face turning red and splotchy as the demon choked the life from him. Castiel had no choice.

"Sam, close your eyes!" He waited the split moment for the Winchester's eyes to snap shut before Castiel unleashed his grace. Blinding white light exploded throughout the warehouse. Inhuman shrieks rattled his eardrums as the power of Heaven cascaded over the demons, snuffing out their smutty essences in a single wave.

Castiel felt when he drew the grace back in and the light receded, yet for some reason his vision remained whited out a few moments longer. He turned his head, only to feel as though the floor suddenly slid out from under him. Castiel gritted his teeth and held perfectly still, willing it to pass. His stomach lurched with the sensation of falling, only he had no wings to catch the wind and right himself. It didn't matter, he told himself. He wasn't really plummeting through the ether. Just give it a minute.

The haze finally began to thin, and darkened shapes coalesced into the bodies of demons strewn about the floor, eyes burned out of their sockets. Sam stood with one hand braced against the wall, the other rubbing his throat. He cast his gaze around the corpses and finally looked at Cas.

"Thanks," he said, voice hoarse.

Castiel didn't even nod in response. His head was vibrating painfully, and he figured any minute movement would send him back into that vertigo spin, which he desperately wanted to avoid.

"Dammit," Sam muttered, and smacked the wall. Scooping up Ruby's knife, he pivoted toward the exit. He'd made it across the threshold before noticing Cas hadn't moved to follow.

"Cas, let's go. Dean could still be in the area."

Yes, Sam would want to get back to hunting down his brother. That's what needed to be done, but Castiel couldn't help at the moment. It was taking every ounce of strength and willpower simply to remain standing. He knew he shouldn't have used his stolen grace like that. It was burning out and taking him with it—using his powers only exacerbated the process. And though he had hoped to save his energies for when they finally found Dean, he couldn't have let Sam die.

But now he could feel the fiery flush brimming within his vessel. Castiel needed to rest, to recuperate, and he'd rather not slow Sam down while he did so, for the Winchester was right: Dean might still be around.

"You…go ahead," he managed to say without too much quavering in his voice. Pain lanced through his chest as he inhaled, and he swallowed an audible gasp. "I will stay…and look for clues."

Sam huffed, but didn't argue. "Yeah, fine. See you back at the bunker?"

Castiel nodded slowly, and Sam's figure was momentarily swallowed by white fog. Yet he kept his features schooled as though nothing was wrong, the way he'd learned from Dean. Oh, how far they had all fallen.

Cas heard Sam's retreating footsteps before his vision had fully cleared again, and then the sound of the Impala's engine as it rumbled to life. Once the vibrating echo faded into the distance, Castiel attempted to take a step forward. Pain stabbed through his temple, and he a shot a hand up to brace it. Heat radiated through his palm to clash with the temperature already spiking in his forehead. He needed to rest, but not here, not among so many dead demons. Mustering his strength and determination, Castiel began shuffling toward the door.

Each step sent a new wave of pain and dizziness through him, and he was half-blind from white spots darting across his vision as he finally made it outside into the cool afternoon air. It did little to soothe the heat churning within his grace, however.

A field neighbored the warehouse, so Castiel slowly made his way toward it, simply to find a quiet place out of the way where he could collapse. He only made it to the edge before pitching forward and catching himself against a large oak. Bracing his hands on the coarse trunk, he twisted around to rest his back against it, and slid down to the ground.

Castiel tipped his head back and sighed. He had hoped to recover from expending his grace like that, but it seemed that was no longer possible. The chain reaction had started. He closed his eyes, full of so many regrets. He would not see Dean Winchester again, would not be able to help Sam find his brother and save Dean from the monster he'd become. He'd managed to restore one family, but at the cost of the one he cared most about.

Sam stopped for supplies on his way back to the bunker. Those first few weeks Dean had been missing and Sam hadn't known what had happened to his brother, he'd ignored necessities like food and sleep. Then once he'd found out that Dean had become a demon, he'd gone crazy trying to find him, summon him, anything. Those were some dark times, where Sam had gone down roads he never thought he'd willingly embrace. All with no results.

Only after a month did he realize he was playing a long game, and he needed to take care of himself if he was going to have any chance of winning.

As he exited the store with arms full of grocery bags, Sam stopped short at a petite brunette standing by the Impala.

"Sam Winchester," she greeted.

"What do you want?" he practically snarled. After the angels had gone back to Heaven, he'd hoped never to see one again. Aside from Cas, of course.

Hannah tilted her head as though in sympathy, which only fueled his ire. "I'm looking for Castiel."

"He's not here." Sam moved forward, attempting to push her away from the car so he could get in, but she remained a statue.

She frowned. "He said he was coming back to earth to help you."

"Yeah, well I meant he's not here right now."

"Where is he?"

"Look, why don't you just leave me a message to give him?" Sam snapped. Honestly, if the angels were having more problems, he'd rather Cas not know about it. Sam needed his help to save Dean; if Cas rushed back to solve whatever Heaven crisis had popped up now, Sam wasn't sure he could handle it. He was barely holding on as it was.

Hannah sighed in exasperation. "I don't have a message. I wanted to check on him, see if he'd found a way to replenish his grace."

Sam paused. He'd forgotten Cas's stolen grace was burning out. He'd been so focused on Dean. They both had. In fact, Cas hadn't stopped looking for a way to help Dean. Which suddenly begged the question—how was he also looking for a way to help himself?

"He's fine," Sam said, though less caustically, and perhaps with less confidence as he thought back on the past several weeks he and Cas had been hunting Dean. Cas had been fine…right? Sam honestly couldn't draw a clear picture of Castiel in his mind. He'd been solely focused on his brother.

Hannah's brow furrowed. "Well, as I said, I only wanted to check on him. He did Heaven a great service exposing Metatron."

Sam's jaw tightened. He wanted nothing more than to kill Metatron himself. But the douche-angel was locked up in Heaven's prison, out of reach.

Sam cleared his throat. "I'll let Cas know."

Hannah hesitated a moment before giving a small nod, and then walked away.

Sam climbed into the Impala and drove back to the bunker where he immediately pulled out his laptop to begin tracking demon activity. Only, he kept getting distracted with thoughts of Cas. What was the state of his fading grace? Cas had smote all those demons in the warehouse today without a problem. Except…Cas wouldn't admit if using his grace like that had weakened him, and dammit, Sam hadn't even bothered to ask if he was okay afterward. He'd been caught in a red haze of fury and frustration over not finding Dean.

Sam leaned back and ran his hands through his hair. He shouldn't have shelved Cas's problem so carelessly. Yes, finding his brother was important, but Dean clearly didn't want their help. Not that it would stop them, but this was a long game. Which meant Sam not only had to take care of himself, but Cas too.

Turning away from the news reports, Sam went to the catalog cabinet and began searching for materials related to angels and their grace.

Castiel was burning. Flaming tongues lashed through his chest and licked across his limbs with the ferocity of hellfire. Tremors wracked his body as the grace inside him spritzed with dying spasms.

No, he pleaded to a God who had never been there. It's too soon.

He hadn't completed his mission, hadn't saved Dean Winchester. That's where it had all started—rescuing Dean from Hell. From that moment when Castiel had first laid eyes on that human soul and gripped it tight, his journey had truly begun. He'd rebelled against Heaven for two boys, had fought beside them, had done terrible, unforgivable things in order to protect them. And now it had come full circle. Dean was a demon. All of Castiel's efforts had been in vain.

Yet he clung to the belief that Dean could still be saved. He didn't know how, nor would he be around to find out. But it was that hope he clung to desperately as the fires of his stolen grace burned away his essence. He was afraid to die, he admitted bitterly. Every death he'd experienced in the past few years had been torment, not just in the moments of oblivion, but also the resurrections that followed. He'd been given far too many second chances and failed at every one. And this time, he knew deep down there would not be another.

Castiel leaned his head back against the tree to gaze up at a midnight canopy speckled with stars. Some humans believed that when they died, their souls rose into the sky to become a star, that they could watch over their loved ones from afar. Castiel liked that idea, even though he knew it to be false.

His vision began blurring again, turning the white pinpricks into elongated diamonds of lightwaves. It was beautiful, and if Castiel held very still, he could almost hear the symphony of the cosmos. He supposed this was a final blessing, to die in peace.

A shadow moved above him, blotting out the stars. It took Castiel a moment to realize it was not a cloud, or his own blindness, for a slight disturbance of air marked when a figure knelt down in front of him. Castiel tensed, sending jolting fire through his joints. Perhaps a demon had come to check on the results of the ambush. Every fiber in Castiel's being urged him to fight, but he had no strength. And wouldn't a quickly delivered, killing blow be easier than dying by fire?

The figure squatted in front of him, not making a sound. A long moment passed in which Castiel began to wonder whether he was hallucinating, but then the person reached a hand into Cas's coat pocket and pulled out his cell phone. A flicker of uncertainty flashed through him. Maybe it wasn't a demon after all, just a mortal vagrant. Cas wanted to say that he had nothing else of value on him, but his throat felt constricted and he couldn't get his lips to move. Everything burned.

The stranger tapped the phone's screen, sending up a faint glow from the LCD display. Castiel squeezed his eyes shut against the harsh brightness, even though in the back of his mind, he knew the emitted light was rather faint. He wished the drifter would just leave. Who sits in front of a dying man and plays with his phone?

Fingers rapped across the virtual keyboard, and a moment later, Castiel felt the weight of his phone slip back into his pocket. He blinked in confusion, but his vision couldn't make out more than a dark silhouette as the stranger stood. After another long moment of staring down at Cas, he finally turned and melted into the night.

Castiel lolled his head to the side, pressing his burning face against the night-chilled tree. Feverish heat stole through his skin to seep into the bark, turning it into the feeling of burning coals scraping his cheek. Convinced it was a mere dream, his eyelids slid closed as Cas sank into a fiery abyss.

Sam had been scouring the Men of Letters' books for the past four hours, and hadn't come upon anything relating to an angel's dying grace, stolen grace, or burning grace. The only thing he read that rang a bell had to do with the power of souls acting as a sort of battery charger. Sam remembered when Cas had sent him and Dean back in time to get the phoenix ash, and how apparently Cas didn't have the juice to bring them back, so he had to "touch" Bobby's soul to power up. So maybe doing that again would give Cas the boost he needed to keep running on that stolen grace. Not that Sam was looking forward to that. When Cas had stuck his fist into Sam's chest looking for a soul that wasn't there, it had been excruciating. But still, if it meant Cas would live longer…

His phone pinged and Sam pulled up a text from said angel.

"At the warehouse. Hurry."

Sam's heart leaped into his throat. Had Cas found Dean? Dammit, why couldn't he have texted that! Snatching up his duffel with the syringes and supplies needed to cure a demon, Sam bolted for the door.

He tried calling Cas as he sped back toward the old warehouse, but the angel didn't answer. Sam swore again, frustration and hope warring within him. This had to be it; he'd finally get his brother back.

As he pulled down the single lane road, the car's headlights bobbed along a large oak…and what appeared to be a body slumped against it. Sam's breath hitched. Shit, that hadn't been there when he'd left.

He threw the car in park and scrambled out, catching a clearer glimpse of a tan trench coat. "Cas?"

Sam darted over and dropped to his knees in front of the angel. In the beam from the headlights, Sam could see Cas's skin glistening with sweat. His eyes were closed, head slumped to the side. Breath wheezed from his chest in rattling bursts. Sam reached up to pat his cheek, only to find his skin blistering hot.

"Cas!" he called, gripping his shoulders and shaking him, but there was no response. Sam craned his neck around. The place appeared as empty as when he'd left. No Dean. Just Cas, burning up with a fever that would melt a human's internal organs. Burning up… Shit.

Sam shook his shoulders again. "Cas, dammit, wake up!"

A tremor ran down Cas's frame, eliciting a pained moan, but still he did not wake. No, this couldn't be happening, not this soon.

Slinging one of Castiel's arms over his shoulder, Sam hefted the angel up and half-carried, half-dragged him to the car where he slid him into the backseat. Then he hurried around to the front and booked it back to the bunker, berating himself—and Cas—the whole way.

Why hadn't he figured Cas using his grace to smite the demons earlier had been a bad idea? Why hadn't he stuck around to see if Cas was okay? Why hadn't Cas said anything? What was his plan, to just stay there and die with Sam being none the wiser? How could Cas do this to him? After everything, Sam could not lose someone else.

Stupid, son-of-a-bitch, idiot.

Sam went through a whole list of other names before arriving back at the bunker. He pulled a still unconscious Cas into a fireman's carry and brought him down to his room. As far as Sam knew, Cas never used the bed, except that one time he'd convalesced after Crowley had shot him.

Sam gently laid Cas on the mattress. His back and shoulders were sweating from being in close contact with the angel's feverish body. Stepping back, Sam gazed down helplessly. There was nothing he could do. Just like with Dean. Why couldn't Sam save those he cared about? Why did everyone leave him rather than asking for his help?

No, he refused to let this happen. Sprinting back upstairs, Sam snatched up one of the books he'd been reading, the one mentioning the power of souls. It described a ritual for binding a soul to someone. Oftentimes it served as a means of controlling the one who was bound, but it could also be used to share energy. And that's what had given Cas a power boost in the past. Sam didn't have time to think of the consequences; his only goal was saving the life of the last friend he had on this godforsaken earth.

With book in hand, he hurried back to Cas's room. The angel looked deathly pale, hardly breathing at all. Sweat plastered his hair to his forehead, and the only sign he was still alive were the occasional twitches running through his facial muscles. Sam figured he didn't have much time.

He pulled a chair up to the side of the bed and laid the book in his lap, open to the page with the incantation. Taking a deep breath, Sam recited the ancient words. He didn't know their meaning, but he felt the air tremble with power as they summoned a deep form of magic.

A ping tugged at something within Sam's chest, not quite painful. More like a buzzing sensation. He looked down and sucked in a breath as a golden cord slithered out of his sternum. It bobbed in the air like a snake as it undulated toward Cas. Lifting its head up, it suddenly plunged into the angel. Castiel's back arched and a huge gasp tore from his throat. Sam felt the string snap taut, reverberating down into his core. He gripped the chair's armrests and breathed as a thousand tingles raced along every nerve ending. They petered out just as quickly, and Cas fell limp again.

The golden cord flickered and faded, yet Sam could still feel something there. A line tugging him toward Cas. Only nothing was happening. Where was the burst of energy that would bring Cas back from the brink of death? Yet the angel remained ashen and unconscious.

"No." Sam gripped Cas's arm, wincing at the heat radiating up through the layers of clothes. Cas was burning up, literally. Would his grace explode in a blinding fireball that would incinerate Sam if he stayed in the room? Not that Sam was gonna let Cas die alone.

"Come on, Cas," he begged. "Don't quit on me now. I need you, dammit." Sam felt moisture prickle the corners of his eyes. He couldn't take this, not again.

"Dean needs you. I can't do this on my own. Please, Cas." Sam dropped his forehead on top of his hand, squeezing Castiel's arm as though he had the power to physically keep him there.

After a moment, Sam felt a different kind of warmth beneath his palm. Not burning like Castiel's fever, but pulsing like a summer breeze. Sam snapped his head up to find his hand had started to glow. A golden hue spread around his fingers to encase Cas's arm and seep into the angel. Sam watched color gradually return to Castiel's face, filling in the sunken shadows around his eyes. His tremors ceased, and the lines of pain etched into his face smoothed out. Sam's shoulders drooped slightly as weariness settled over him, but he didn't stop. He placed his other hand against Cas's forehead. The amber luminescence spilled forth again, pushing the fever all the way down until Cas's skin felt normal beneath Sam's palm.

Tentatively, Sam pulled his hands away, and the golden radiance faded. The connection was still there; Sam's soul was still bound to Castiel, but apparently the energy transfer required physical contact. That was good. Sam could give Cas life boosts as needed without draining either of them.

Cas let out a soft moan and his eyelids fluttered.

"Cas?" Sam leaned closer.

Castiel opened his eyes and blinked dazedly. "Sam?" he rasped. His gaze traveled around the room uncertainly before settling on Sam. "I…don't understand. What happened?"

Sam let out the breath he'd been holding. "You were dying. I barely got to you in time." He shook his head and growled, "You should have texted me sooner, or better yet have told me from the start that smiting all those demons had weakened you!"

Cas's brow furrowed and he was silent for a beat. "I…didn't want to burden you. I thought, perhaps, I would recover." He glanced down at his chest, frown deepening. "What have you done?"

He straightened. "What I had to. I'm sorry, Cas, but I'm not losing you too."

Castiel looked up sharply. "Sam, no. I can't ask this of you."

"You didn't. And if you had, my answer would still be yes."

Cas started shaking his head. "I don't know what the long-term effects of this will do to you—"

"Don't," he interrupted. "I need you, Cas. I'm sorry I haven't been paying attention, that I've been so focused on Dean."

"He's your brother."

"So are you." Sam clasped Cas's hand, feeling once more the pulse of warm, golden light between them. It didn't feel draining though, not this time. Cas's essence had been restored, and for the moment, the two of them were holding each other in a precarious balance as both teetered on the precipices of death and despair.

But Sam had succeeded in saving one person he cared about, and it gave him hope. He was going to put his family back together—his whole family. One piece at a time.