A/N: And the saga continues. Lots of Sam and Cas friendship in this one.

THEN

"What will you do now?"

"I need to find my brother." Dean Winchester shifted his weight, his aura radiating uncertainty as he gazed out upon the apocalyptic landscape that had once been the Earth he'd known. Smoke rose from ravaged towns; the sky was murky with it.

Castiel considered this human he had just rescued from the Pit, an act which had been more of a whim than anything, though something inside him had been struck by the sacrifice he'd witnessed, this mortal hunter holding off the hounds of Hell so his brother could help other humans escape.

War had started, but Castiel no longer had a place in it; he had turned his back on Heaven's creed, which had somehow shifted from their original mandate to one of violence and bloodshed. Castiel wanted to uphold the duty he knew was right—protecting humanity. He just didn't know what one single angel could do in the face of such odds.

But, perhaps…he could start with one.

"I will help you find your brother."

…

"Why'd you rescue me from Hell?" Dean asked one night when they'd made camp in a culvert up on a ridge of a park. Fires glowed in the town below, punctured by the echo of gunfire.

Castiel briefly flicked a look down at the human from where he stood watch at the mouth of the foul smelling drain, canting his head in confusion. "You deserved to be saved."

"No offense, and I'm not saying I'm not grateful, but you didn't even know me."

"Why did you sacrifice yourself for those people at the Devil's Gate?" Castiel countered. "You didn't know them."

Dean's mouth quirked. "Touché."

…

"Cas, let the squirrel go."

"It was attempting to steal your food," Castiel replied, holding the rodent by the back of the neck.

"I thought angels were guardians of animals, too."

"Do you want to share your food?"

Dean huffed. "No."

Castiel didn't think so. Nourishment was scarce enough as it was. He lifted the squirrel to eye level. "Human food is bad for you," he said, before setting it back down on the ground.

It bolted away and scampered up a tree to a high branch, then turned around to chatter angrily down at them.

Dean crossed his arms with a smirk. "Yeah, you told it."

…

Two months later, they found Sam Winchester, and Castiel watched in slight bafflement as the younger hunter immediately splashed holy water in his brother's face. Castiel supposed the caution was warranted, though, given Sam had last seen his brother being dragged into Hell.

Dean voluntarily cut his arm with a silver knife. "It's me, Sammy."

Sam's expression slackened in dismay and sheer relief, and the two embraced in a fervent hug. Then Sam cast a curious look at Dean's companion.

"This is Cas. Castiel. He's an angel. Turns out they don't have halos or harps."

"Oh my god- uh, I mean," Sam stammered, eyes wide with a wonder Castiel had rarely seen from humans in over a century.

The young man stuck his hand out eagerly, and Castiel stared at it for a moment before he realized he was probably supposed to take it. He reached out to accept the gesture, placing his other hand over their clasped ones.

"It's good to finally meet you. Dean has talked about you a lot."

And then he sensed it, something dark and disquieting nestled like a seed deep within this young man's very blood.

…

"You sure you don't want to come with us?" Dean asked.

Castiel fidgeted. "I appreciate the offer, but I'm a soldier. With the Devil's Gate open, there are many demons to fight."

Dean nodded sagely. "Don't be a stranger, though, okay?"

"If you need me, I'll be able to sense it, and I'll come find you," Castiel assured him. He glanced over to where Sam was packing up his gear from a nearby cabin. He hesitated. "Dean, there's something about Sam…" Castiel didn't how to come out and say it.

Dean just looked at him sadly. "So you noticed, huh?"

Castiel furrowed his brow in confusion. Dean knew?

"Guess I kinda figured you might. The demon that killed our mom…she walked into Sammy's nursery and found it feeding Sam his blood."

Castiel's eyes widened in alarm.

"Cas, please don't…" Dean began desperately.

"I would never hurt your brother," he quickly said. Besides, despite the evil signature lurking beneath the surface, Castiel had also sensed goodness and a pure heart. So he did not consider Sam Winchester an evil abomination to be dealt with.

No, the only thought on Castiel's mind, was why?

…

NOW

Castiel gazed out the cabin's window at the campgrounds and the mundane activities people were milling about with outside. Life at Camp Chitaqua continued as normal, it seemed, while the atmosphere inside the Winchesters' cabin was heavy with a pall of foreboding. Dean had just finished recounting the events with the "Khan worm," as he called the demonic slug that had invaded people's bodies. All with the mission of retrieving Sam.

Castiel couldn't deny he was very disturbed by this, for multiple reasons. With the Apocalypse already under way, there was no reason the demons should be interested in one single human. It had also been years since Sam had been contaminated by demon blood, and the demon responsible was dead, so who was coming after him now? But above all, Sam was Castiel's friend, and he did not like his friends being threatened.

He turned back to face the brothers. "I have no idea why demons would want Sam," he began. "Though, I can only guess it has something to do with the demon blood."

Sam's gaze was fixed on the floor, his entire posture hunched in his chair and radiating distress…and guilt. It made Castiel's heart ache that this young man should feel responsible for something that was done to him when he was nothing but a child.

"I will do my best to look into it," he promised them. Stepping closer to Sam, he added, "In the meantime, I can carve a protective sigil into your ribs, one that should hide you from demons and prevent any further possessions like the one you experienced."

Sam finally looked up, shaking off some of his despondency in exchange for confusion. "Carve into my ribs?" he repeated dubiously.

"It's a simple matter," Castiel replied. "Though, it may hurt for a moment."

"Sam," Dean said softly from where he was standing near the door.

Sam swallowed. "Yeah, okay. Um, maybe Dean should get one, too. Just to be safe."

"The demons aren't after me—"

"No," Castiel interrupted. "Sam's right."

Dean rolled his eyes, but nevertheless came over to stand next to his brother.

Sam got to his feet. "What exactly—"

Castiel pressed one hand to each of their chests and summoned a flicker of his grace. The procedure only took an instant, but both brothers nearly bent double with a strangled sound of pain in their throats.

"What the hell, man?" Dean gasped.

"I did warn you it would hurt."

Dean clenched a fist against his sternum. "It felt like you branded us."

Castiel just canted his head at them. He'd said he would carve the sigil into their ribs…

Sam sucked in another breath as he tried to recompose himself. "So, uh, how are you going to find out anything? I mean, Yellow Eyes is dead."

Dean straightened sharply. "Yeah, but Meg's not."

"Who?" Castiel asked.

"Yellow Eyes had two demon minions," Dean explained. "He called them his 'children,' Tom and Meg. Tom is dead, but we only exorcised Meg. And since the Devil's Gate opened, maybe she's made her way topside again. She might even be the 'her' the Khan worm mentioned."

Castiel furrowed his brow in thought. Interesting. But if anyone knew what this "Yellow-Eyed demon" had been up to, it would be someone who'd been close to him.

"Then I'll start by trying to track her down," he said.

"I want to come," Sam spoke up.

Castiel blinked in surprise.

"Uh, Sam, I don't think it's a good idea for you to go looking for the guys gunning for you," Dean said.

"Dean's right," Castiel put in. "And I'll be able to find information faster on my own."

Sam's jaw tightened. "This is my life, and I'm tired of feeling like some…unclean thing. A demon ruined our lives, Dean. And now they're coming back to use me as some sort of pawn in a war I don't even understand?" He shook his head, expression pinching with anguish. "I deserve to know why."

Dean looked away, his own eyes taking on an unshed sheen. After a long moment, he reached a hand up to rub the back of his neck, and looked to Castiel as though giving him the final decision.

He turned his attention back to Sam, who was gazing at him pleadingly. Castiel could understand the young man's turmoil, and Sam was right; this was his life, and it had been tampered with by forces greater than his understanding. And he deserved to find answers.

"Alright," Castiel said.

Sam let out a breath of tension, seeming surprised at the capitulation. He gave Castiel a grateful nod.

"I could transport you through the ether with me," he began. "But it will be unpleasant, and I don't recommend frequent trips, as humans can asphyxiate on the celestial atmosphere. I suggest we use human means of transportation."

Sam nodded, jitteriness now rolling off him. "I'll go gas up one of the jeeps."

With that, he hurried out the door.

Dean shook his head and turned away.

"I'll watch over him," Castiel assured the older Winchester.

"I know."

Castiel started to leave when Dean spoke up again.

"And, Cas." The hunter gave him a wan yet sincere smile. "Glad you made it back."

Castiel returned the small smile. He and his garrison had failed to close the Devil's Gate and stop the Apocalypse…but he was glad to be here now when the Winchester brothers needed him. He'd personally taken up the mantle of guardian for Dean and Sam, and Castiel would do everything within his power to protect them.

Once he was behind the wheel and on the road, Sam felt some of his pent up energy start to settle into a steady rhythm synced with the rumble of the jeep's engine. Just the fact that he was doing something, even if they didn't actually have any leads yet, gave him a firm focus and purpose.

He glanced at the angel in the passenger seat. "So, uh, how are we going to find Meg?"

"I suggest we capture a humanoid demon and interrogate it," Cas replied.

Sam shrugged his brows. "Shouldn't be too hard," he muttered, and took the highway leading into the city that angel Zachariah had tried to nuke because of its heavy demon infestation. The trick, of course, would be to find one of the humanoid ones, like Cas said, and not the beastly monsters the Pit had also spat out onto Earth.

Sam parked the jeep on the outskirts of town; there was greater risk of drawing attention if they took it further in, so they'd have to proceed on foot. He got an MP5 sub machine gun loaded with angel bullets out of the back. Cas waited patiently until he was ready, almost looking like some kind of futuristic soldier in his dark jeans and zipped up black jacket and carrying no weapons at all.

Because he was one.

"The kind of demon we need would probably be holed up in a place of luxury," the angel said. "I've noticed they seem to enjoy liquor as much as Balthazar does."

Sam's mouth quirked. "I know of a bar a few blocks over. We can start there."

He missed the days of Wi-Fi and Google maps to look up addresses. If they didn't find a demon at the first location, they'd have to resort to a grid search, which would be more time consuming and dangerous.

Sam led the way, keeping his eyes peeled along the broken and shattered windows of the surrounding buildings for things creeping within. Fortunately, he knew most of the demons preferred the center of the city, so they shouldn't run into any hordes just yet.

The Roark used to be a fine pub with good food and good beer. Sam had only been a handful of times during his time on the road with his brother, but the place had made an impression. It was a shame to see it now, windows boarded up, authentic oak door covered in gouges from frantic claws. Trash littered the sidewalk out front.

Cas came to an abrupt halt. "There's warding against angels here," he said.

Sam straightened with alertness. That meant a demon probably had made himself at home inside. He scanned the street. "I can sneak in and disable it," he said.

He knew what that type of warding looked like, as they had it installed back at Camp Chitaqua. They'd just also incorporated an adjoining sigil with Cas's and a few other angels' names so they could bypass it.

Cas's jaw looked tight. "If you're caught, I won't be able to get in there."

"I've handled demons before," Sam pointed out, and hefted his MP5 for good measure. If worse came to worst, he could simply riddle the repellant sigil with bullets to neutralize it. The demon, they wanted alive.

Cas's shoulders were tense with displeasure, but they had no other means of getting them both inside, and they couldn't wait around for the demon to decide to come out. So Sam gave the angel one last look before heading around the side of the building toward the back entrance.

It wasn't locked; why would it be? Sam grimaced as the door grated open, revealing a dark interior. Taking a deep breath, he ventured inside. The place was musty, air cloying with the odor of alcohol and cigarette smoke. He passed by the kitchen, pots and pans scattered across a floor stained with all manner of substances. The floor of the bar was just as messy, with overturned tables and broken chairs. There was, however, a nice row of empty liquor bottles lined up on the counter. Someone had been busy.

Sam cautiously swept his gun around the room, but it was empty. Maybe the demon had made himself at home in the loft upstairs, but Sam wasn't going to take the time to check. He spotted the warding on the inside of the window boards, done in bright red spray paint, and went straight toward it. Lowering his weapon to free one hand, he reached for his knife and began to slash through the junctures of the sigil.

Something thudded on the floor above him, making him flinch with a burst of terror. He started to hack at the warding more urgently. There…

A bottle clinked, and Sam whirled around, coming face to face with a bearded man a good foot shorter than him. But his eyes flicked black.

"Come in for a drink?" the demon said, mouth cracking into a minacious grin.

Sam scrambled to raise his gun, but before he could get a shot off, the demon grabbed the weapon and wrenched it so hard that Sam went flying. He hit the floor and slid several feet through detritus. Stomping footsteps quickly followed, and then the gun was yanked from his grip and tossed aside. The demon leaned down and sneered.

"It's been a while since I've had some entertainment."

Sam slashed with his silver knife, catching him across the chest and making him lurch backward. It wouldn't actually hurt a demon, but Sam only needed to buy another second…

Cas zipped out of the ether, fist wreathed in crackling blue electricity, and delivered a sucker-punch to the demon's jaw before the bastard even knew what hit him. He crashed to the floor with a loud thud and didn't move.

Sam's chest was heaving from the adrenaline rush, but he lifted his head with a quirked smile at the angel. "See? Teamwork."

Cas just gave him a long-suffering look. "I'll prepare a devil's trap."

He strode around the counter, presumably to find something to draw with. Sam pushed himself to his feet and gazed down at the unconscious demon.

Time to start getting some damn answers.

Dean poured his frustrations into his efforts to sand down the tree stump with the sigil that Khan worm had defaced. It was slow, tedious work, pushing the sandpaper forward over and over again. He'd been at it for hours already, but finally the harsh lines and gouges were beginning to smooth out. Once it was completely gone, they could mark it with the protective warding again.

"Shouldn't that be the swabbie's job?" someone called.

Dean stiffened, one hand immediately going for the gun laying on the ground beside him when he didn't recognize the voice. He paused before drawing it, however, as he took in the lone figure standing six feet away, hands in the pockets of a brown leather aviator jacket, complete with the wide, fur-lined collar folded down the shoulders. All that was missing was the sunglasses.

"Gabriel," he said, somewhat surprised. "What brings you here?" They hadn't had a visit from the archangel since Cas had brought some of his garrison to Camp Chitaqua as a kind of 'get-to-know-your-charges' field trip.

Gabriel shrugged both shoulders and walked closer. "Wanted to see what's always drawing Castiel away." He swept his gaze over the campgrounds.

Dean slowly stood up, wiping the back of his arm across his sweaty brow. "Uh, Cas isn't here."

"I know." Gabriel turned a shrewd gaze back to him. "He sent me a message about his little outing."

Dean didn't say anything, not sure what the angel had come here looking for.

They held that silent stare for a prolonged moment before Gabriel broke it, shifting his gaze down to the tree stump.

"I also heard you had some trouble with the wards."

Dean continued to eye the archangel warily. "Yeah. Could've been worse, though. Khan worm just got to three."

Gabriel arched a brow. "Khan worm? Nice. I personally like to call them Goa'uld."

Dean quirked a confused brow, to which the angel rolled his eyes.

"Really? You never watched Stargate?"

"I was more of a Dr. Sexy kind of guy."

Gabriel pursed his mouth and canted his head in apparent appreciation. Nice to know some angels had bothered to watch television.

"I'm surprised," he went on, starting to pace around the stump. "I thought you'd want Castiel to fix these."

"He left me a notebook with the sigils to carve," Dean replied. "I can do it. What are you really trying to ask here?"

Gabriel's eyes narrowed a fraction. "Like I said, I'm curious why he's so intent on always checking up on you. We took every measure to ensure you could make a self-sustaining home here."

Dean bristled at the veiled disapproval. "Cas is my friend."

"Ye-eah," Gabriel drawled. "It's just, that ain't exactly normal, you know."

"I thought your little private army was all about protecting humans."

"Protect. Not get chummy with."

Dean crossed his arms. "Well, Cas is different."

Gabriel nodded thoughtfully.

Dean waited for several beats to see if this impromptu interrogation was over.

Finally, Gabriel shrugged dismissively and plastered on a debonair grin.

"I'll give you a hand with the warding."