Being possessed by an angel hurt.

'Like being chained to a comet' was an apt description. For Cass, the flood of Castiel's blue-hot grace into her body was like looking into the sun. It burned, and blinded her, and made her feel raw and blistered not in her body, but in her soul. She wanted to close her eyes, to curl into a protective little ball and shut it all out. She might even have been able to—in her head, she could feel Castiel's presence gently ushering her into a corner of her own mind, where she would not have to observe what was about to happen and where the scorching heat of Castiel's grace would not be so utterly devastating.

But somehow, that terrified her even more. To be possessed by an angel was a terrible thing, but to be isolated in a corner of her own mind while it happened, not knowing what was happening or if Castiel succeeded, was worse. So Cass ignored Castiel's gentle nudges and planted herself at the forefront of her mind, not fighting for control, but insisting on remaining awake, present, and watching. Castiel hesitated, but did not fight her. Slowly, reluctantly, Cass sensed him shifting, rearranging his occupation of her vessel so that she was in something like a passenger seat—able to observe the goings-on outside through her own eyes, but unable to control the direction of her own body.

The return of her vision was disorienting. Dean and Bobby and the hospital room were already gone, and everything around her was a whirl of color. Cass guessed that this must be what flying was like, but it didn't feel at all like she'd thought it would be. It didn't feel like flying at all. It was more like she was a central, fixed point in the universe, and space and matter were rushing past and reshaping all around her. She was all at once moving impossibly fast and standing utterly still, and if Cass had still been the one in charge of her own bodily functions, she would have crumpled to the ground and vomited from the overwhelming experience.

And then, abruptly, the motion ceased, and Cass was standing in a world of shadow and fire. The sheer heat of the place made Castiel's grace feel like pleasant afternoon sunshine. If her body wasn't protected by Castiel's powers, Cass was sure she would have burned to a crisp as soon as she set foot in the place. But she was, and she didn't.

Together they stood before a massive gate. What it was made of, Cass could not say. In one glance it might have been cast iron, but at second glance she thought that it looked more like bone—blackened, human bone. But her eyes, directed as they were by Castiel, did not linger long on the gate itself. Instead they fell on the dozen figures standing before it.

They were all shaped like people, but they were none of them human. More than half of them were demons, their warped, putrid souls twisting around them wildly. The remainder were angels, bright to Castiel's eyes, with light impressions of their true forms overlapping their human shapes. They were tall, many-eyed, many-limbed things composed of starlight and grace, and if Cass was in charge of her own body she would have screamed at the sight of it because it was too much too look at, more than her human mind had ever been designed to comprehend—

But she was not in charge of her own body. Castiel strode forward on Cass's feet, strong and purposeful and unphased by the difference in their numbers.

"Castiel," said one of the angels. It had not advanced to meet them. It seemed frozen, uncertain and staring. "Possessing a prophet? Is there no blasphemy you won't sink to?"

"You have no right to speak of blasphemy," said Castiel through Cass's lips. Their voice was lower, colder, more rough than it had ever been in her life. Castiel flicked their wrist, and suddenly there was cool metal in their hand, and sorrow and anger in their heart. The emotions came from Castiel, not Cass, borne from the knowledge that these angels, his brothers, were now his enemies, and that he was prepared to kill them if he had to. But the sorrow was shared in its entirety, in the same way that Cass's vessel was shared in its entirety.

They said, "Let me pass."

The angels did not move at first, instead trading looks with each other. Then, in unison, they backed away from the gate, standing aside to clear the way. The demons, left without backup and faced with an avenging angel, looked much less confident. Half of them scattered, following the angels' example, but a few remained, sneering at Cass and Castiel with their corrupted faces and preparing for a fight.

Castiel moved them forward, unconcerned by the presence of the demons. The closer they came to the demons, the brighter the world seemed to get. There was a humming in the air like electricity, a smell like ozone overwhelming the smell of sulfur.

From the side of the gate, one of the rebel angels called out sharply, "Stay back, filth! Do not touch her—do you want to bring Michael down on our heads?"

The demons did not have time to heed the angel's words. Castiel surged forward, planting their angel blade between one demon's ribs, then another, then another. Each of them died with a flare of red light and then disintegrated into something less than dust. The last demon Castiel seized by the throat, but did not stab, instead planting the shining angel blade against its tortured, pitch-black soul and demanding, "Where is Sam Winchester?"

The demon raised its twisted, rotten arm and pointed a shaking finger past the gate and toward the left. The angel blade slid home, and then Castiel was striding forward through the still-dissipating mist of its body.

They descended into Hell. Before them, demons shrank back from the brilliance of Castiel's grace. Those who did not, or did not retreat quickly enough, were treated to the same interrogation that the demon at the gate had received, and met the same fate. They moved quickly through the winding labyrinth of flesh and fire and bone, and then, at last, they found Sam.

His soul was behind another gate of blackened bone, chained to a wall and looking defeated, but unharmed. At the grunts and dying flashes of his demon guards, Sam looked up from staring at the floor, expression melting rapidly from stubborn rebellion to wide-eyed disbelief.

"Cass?"

"Right on two counts," Cass thought, and was surprised to hear the words emerging from her mouth in her own voice, her lips twisted in a wry smile. But then her lips pulled downward and Castiel said intently, "We have to go."

Castiel tore apart the chains around Sam's wrists as if they were made of tissue paper, and then he grabbed hold of Sam's arm. Cass could feel his wings spread in anticipation of flight and for a moment marveled at the disorienting feeling of using a limb that she did not truly possess. She braced herself for the dizzying rush of flight, but it did not come. Instead, there was a solid kick to her side that sent her rolling across the super-heated floor.

It was Uriel. Again. Of course.

"Very clever, Castiel," he said, advancing slowly with an angel blade in his hand. "Using the prophet as a human shield. Vulgar, but clever." He shook his head. "I told them we should have killed you, and picked a different messenger."

"You are already a stain on the name of Heaven," Castiel ground out. "Attack the prophet again and the archangels will grant you no mercy."

Uriel did not blink. "I'll risk it."

Uriel surged forward, blade flashing. Castiel thrust Cass's arm up into an immediate parry, the blade clashing. Even though she was awake and aware, Cass could hardly follow the fight, the quickness of Uriel's movements and Castiel's counter-attacks throwing her off. Castiel and Uriel were locked in a lightning-fast, deadly whirlwind, blades crashing and clattering against each other.

Almost immediately, the whole world began to shake. When the blades first touched it was little more than a rumble, but as time went on the walls around them shook more and more, and Cass knew from Castiel's own certainty that this was the approach of either Michael or Raphael, sensing the imminent danger to the prophet. Uriel knew it, too, and grew more desperate. The desperation gave him strength and speed, and with a quick swipe, he delivered a deep slash to Cass's right arm. Castiel's angel blade went flying and Cass cried out as they were kicked in the chest and sent skidding along the ground.

Cass hissed, and she and Castiel scrambled up onto their knees and Uriel advanced, angel blade poised with deadly purpose. The room was positively vibrating now, so fierce was the shaking. The archangel must be very close, now. But was he close enough?

Castiel raised their head and said lowly, "They will kill you for this, Uriel."

Uriel hefted the blade and said simply, "Then I will have earned a worthy death."

He drew his arm back. It was only because Castiel was still controlling her body that Cass saw what happened next. While she wanted to close her eyes, to flinch away and not watch the coming blow, Castiel was facing Uriel head-on, defiant to the end. Because of this, Castiel and Cass both saw the bloody glint of silvery metal as Sam thrust Castiel's fallen angel blade through Uriel's ribs.

Castiel's horror was immediate.

"No!" Castiel scrambled up and took hold of Uriel's shoulders. Uriel, meanwhile, was smiling bitterly, even as the light left his eyes.

"You've failed, Castiel," Uriel said darkly, blood bubbling at the corner of his lips. "The seal is broken." And then the light left his eyes, and Uriel slumped, dead weight in Cass's arms.

Cass reeled, paralyzed by horrified disbelief. Castiel stepped back and let the body drop, gritting their teeth. He seized Sam's arm roughly, spread his wings, and flew.

Bobby, Dean, and Jimmy Novak all jumped when Cass and Castiel appeared over Sam's body where it had been laid out in Bobby's backyard. Castiel ignored them, pressing Sam's soul into his body and resuscitating him with the tiniest jolt his grace, breathing life back into the body and reestablishing the connection between flesh and soul.

Sam's green eyes shot open immediately and he sat up, gasping for breath. Cass's own deep relief at seeing him alive again mixed and blended with Castiel's overwhelming disappointment over what it cost.

"Sam!" Dean surged forward to check on his brother, to reassure himself that he really was back. Cass would have stepped back to give them some room, but Castiel had yet to grasp the intricacies of personal space and so remained rooted to the spot. Dean, upon confirming that Sam really was alive and breathing again, caught sight of the blood staining Cass's right sleeve. "Are you alright?"

Castiel did not answer the question. Instead he said bitterly, "We failed. The first seal is broken."

"What?" Dean stepped back, frowning at them. "How? I thought Cass couldn't break it? I thought that was the whole point."

"I broke it," Sam said roughly, shame-faced. "I shed Uriel's blood—" He turned to Cass then, his eyes full of frustrated confusion. "But how is that even possible? I'm not… righteous."

"You took up arms to defend your comrade, who also happens to be a Prophet of the Lord," Castiel explained flatly. "You were righteous enough."

Dean grimaced, deciding to ignore the impending apocalypse for a moment as he said, "Okay, it is seriously weird for you to be in her body." He pointed over his shoulder toward the waiting, skittish-looking Jimmy Novak. "Go back to your own vessel."

Castiel furrowed Cass's brow, considering. "I can guard the prophet more easily from within," he said to Dean, and then, to Jimmy Novak, "I know you wished to return to your family."

"I did," said Jimmy immediately. "I do." He swallowed hard and shook his head. "But not if they're still in danger. I'd rather they lived without me, than died with me."

Cass, for her part, was not thrilled at the idea of Castiel staying in her body for an extended amount of time. It was a distinctly unpleasant experience, and one she wasn't keen to prolong any longer than necessary. She could feel Castiel's hesitance, less at leaving her undefended than at giving up the strategic advantage of a vessel that no angel would dare to harm.

You can borrow my body again if you need to, Cass promised him, But only if you need to.

Castiel nodded at that, accepting both the invitation and her restrictions. To Jimmy he said, "Very well."

And then, with a flash of light, Castiel was gone from Cass's mind. Cass swayed, and was glad she was kneeling on the ground next to Sam instead of standing, because she might have fallen otherwise. The sudden lack of heat made her feel suddenly cold, and she shivered even in the summer sun.

"Cass?" Sam reached out to steady her, taking care to touch only her left shoulder and not disturb her bloody right arm. "Are you okay?"

Cass took a moment to stare at Sam's concerned face, taking it all in. The light in his green eyes. The slightly disheveled brown hair. The look of sincere protective concern, tinged by guilt.

Alive.

The first seal had broken, and they would have to deal with that, but Sam was alive, at least. And Cass wouldn't have it the other way around.

"I'm okay." She pulled away from Sam, pushed herself to her feet, and said to the group at large, "The next seal will be the Rising of the Witnesses." She directed her next words to Bobby in particular. "I've got the outline of the spell to stop it, but I imagine you know it better than I do. You'll want to call every hunter you know and tell them the instructions, though. I don't know if it needs to be performed by everyone who experiences it, or if one person doing the spell will end the seal entirely, but we should prepare for the worst."

She was rambling, a little, but talking about what she knew made her feel better, more in control in the face of the knowledge that the first seal had broken, sooner than they had hoped, and despite everything they'd done to try to stop it.

"What's the Rising of the Witnesses?" asked Dean as he heaved Sam to his feet and gave his younger brother a solid pat on the back.

"It's a seal," Cass explained. "The Witnesses are the spirits of those who have died unnatural deaths, come to take revenge on those who failed to save them."

Dean's face darkened. "So it's basically designed to kill hunters."

Castiel, back in the dark-haired, trench-coated vessel of Jimmy Novak, nodded. "It's a good strategy," he said with grudging admiration. "Lilith will try to take out any force which could stop her from breaking the seals."

"I'll get dialin'." Bobby made a bee-line toward the house and disappeared through the back door.

Dean turned to look between Cass and Castiel. "So it's really happening? The Apocalypse."

"The first seal is broken," Castiel confirmed darkly. "It's happening."

"Okay," said Dean, his voice level, clearly trying to stay in control of the situation. "Okay. How long do we have until all the other seals are broken?"

Cass bit her lip. "I'm not sure. Last time it took three, four months? But now, I suspect it'll go quicker. They'll want to get it over with as soon as they can, and with the rebel angels already exposed, they won't be shy about helping to break the seals."

"Then we've got to find Lilith," Dean said resolutely. "Kill her before she can break the rest of the seals."

"Or cure her," Cass reminded him. Dean waved a careless hand.

"Whatever," he said. "We've just gotta stop her."

"We'll have to find her, first," Sam reminded him glumly. "None of our tracking spells have worked, remember?"

Dean turned to Castiel expectantly. "What about you? Can't you find her with your angel powers, or something?"

"My 'angel powers' cannot locate Lilith," Castiel said carefully. "There are ways of hiding even from an angel's sight, as you know." His eyes flicked toward Bobby's house, which even now was warded against his presence. "And with rebel angels on her side, she will be able to elude us even more effectively."

"Great," said Dean, sarcasm heavy in his voice. "Just great. How the hell are we supposed to find her, then?"

Cass grimaced. "I might have an idea… but you're probably not going to like it."

Dean turned to look at her warily. "Alright. What is it?"

"There's a demon who might be able to help us."

"A demon," Dean repeated, disbelieving. "You've got to be kidding me." Cass shook her head.

"Who?" asked Sam, eyebrows raised. "Ruby?"

"No," Cass said forcefully. "No. Definitely still kill Ruby if she shows up again. No, you haven't met this demon yet. He becomes something of an off-and-on enemy-slash-ally to you guys, the way I've seen it. Don't get me wrong, he's not good—but sometimes his ambitions align with yours, and you work towards the same goals until one side or the other decides it's time to stab their partner in the back."

"You're not really selling this. You know that, right?" said Dean.

"Yeah, well, I don't love the idea of contacting him, either" Cass said, frowning. "He's useful, but he's also cunning, and probably the most intelligent demon I've seen. It makes him dangerous. But I think he would be willing to help us, because he's smart enough to know that he's on the hit list if the Apocalypse really goes down, no matter who wins."

"What do you mean?" asked Sam. "The demons work for Lucifer, don't they?"

"Yes, they do. Or at least, most of them do," Cass said. "But Lucifer hates humans. And since demons are nothing more than twisted, warped human souls, he can't totally eliminate humanity unless he destroys all the demons, too."

"But this guy, this demon," Dean said, "he helped us stop the Apocalypse? Before?"

"Yes. He gave you the Colt back, plus more ammunition—before you all learned the hard way that the Colt can't kill an Archangel," Cass explained. "And then, once you realized you couldn't kill Lucifer, he helped you put him back in the cage."

"I don't like it," Dean said stubbornly. "Demons are demons. You said yourself that this guy—"

"Crowley."

"Crowley, is dangerous. You even said he stabs us in the back!"

"I don't like it, either," Cass said sincerely. "But if we can't find a way to track down Lilith ourselves, it might be our only option to find her before all the other seals break."

"I have not fallen so far that I am willing to consort with demons," said Castiel gravely.

Dean turned to him and said emphatically, "Thank you!"

Cass shook her head. "Then I really do hope you can find another way in time."

She turned and re-entered the house, heading upstairs to review her notes again. Maybe, if she stared at them long enough, something would come to her. Some idea that hadn't occurred to her yet, or some solution Castiel and the others would find marginally more palatable than 'consorting with demons'. Witches? Gabriel?

She'd barely spread her notes out across the bed before there was a knock on her bedroom door. The noise made her jump—she was pretty sure that it had taken a few days after the first seal broke before the rising of the witnesses, but with the ever-changing timeline, she couldn't be sure it wouldn't happen sooner. But it wasn't a vengeful ghost at the door.

"Can I come in?" asked Sam through the door.

Cass shut her laptop, but left her notes out. The papers were still written in code, so Sam wouldn't be able to read them even if he wanted to. "Yeah, sure."

Sam cracked open the door. He was holding a small first-aid kit. "I wanted to take a look at your arm."

"What?" Cass blinked, remembering, and looked down at her right sleeve, dark with dried blood. She prodded it without fear—it didn't hurt at all. "It's fine. Castiel healed it already." He must have done so before he even left her body. She hadn't even noticed it happening.

Sam was still eyeing the bloodied sleeve warily when she looked back at him, and then he turned the worried green eyes to her face. "Please?"

She hated that the puppy-dog expression of his was beginning to work on her. She sighed and shuffled her papers out of the way so he could sit next to her on the bed, then rolled up the bloodied sleeve. Her arm wasn't pretty, smeared as it was with dark dried blood, but as Sam cleaned it with a sterile wipe, the skin beneath was whole and unblemished.

"See?" Cass said gently. "Not even a scratch."

Sam didn't look at her. His head was still bowed over her arm, slowly clearing away the last of the blood. When there was no more blood, Sam crumpled the wipe in his hand. "I'm sorry."

Cass frowned at the top of Sam's head. She was tempted to tell him that he was violating their 'no thank yous or apologies' agreement, but this didn't seem like the right time. His shoulders were hunched, his tone filled with quite a bit more self-loathing than was warranted over the arm injury. Which meant, of course, that he wasn't apologizing about her arm, and he believed he'd really, truly fucked up.

"It's not your fault, Sam."

Sam's head jerked up, pale eyes burning with righteous fire. "I broke the seal!"

"None of us could have predicted it breaking like that," Cass said fervently. "We did everything we could." Sam was looking away, his jaw working stubbornly, and Cass nudged his knee to get him to look at her again. "And for what it's worth, I'm glad you didn't let Uriel stab me. You saved my life, Sam. And Castiel's, too."

Sam huffed doubtfully. "He didn't seem that grateful about it."

"He's… going through a lot of stuff right now," Cass said, wincing. Then she forced herself to rally and finish delivering her pep talk. "The first seal is broken, but we all survived to fight another day. That's not nothing."

"But what if we're fighting a losing battle?" Sam's eyes were bright and worried. "What if everything you've seen is just fate? What if this turns out like all those Greek prophecies from myths, where you can't escape what's supposed to happen no matter what you do? Where everything you do to try to change things just makes the prophecy happen?"

"I don't believe that," Cass said flatly. She had never even considered it, and she refused to consider it now. She couldn't. It was too terrifying a possibility to entertain for even a moment. She had to believe that things could change. "And you shouldn't, either. You and Dean already defied fate once in the version of events I saw. I don't see any reason you can't do it again."

Sam didn't look convinced. He'd hunched over again and was now staring at his hands, brooding. Cass sighed.

"Tell me something, Sam." Reluctantly, Sam looked up at her through the curtain of his hair. "If you could go back in time, and you knew killing Uriel would break the seal, would you still do it?"

It was not the first question like this she'd ever asked him, and like before, it was a question she already knew the answer to. Sam knew it, too, his lips twisting briefly into a wry, 'you-got-me' expression.

"Yeah. I would." His eyes flicked to his hands, now clenched into fists, and then back to her face. "I swore I wouldn't let anything happen to you."

"Then there's no sense regretting it, is there?" she asked simply. "We just have to focus on what we can do."

"Finding Lilith," Sam completed the thought.

"Finding Lilith."

Down the hall a loud noise echoed off the walls, and Cass flinched before processing that the noise was just Bobby sneezing. Cass sighed and rubbed the bridge of her nose, then pushed herself up from the bed and crossed the room to the closet, where she began to rummage.

"Uh. Cass?" Sam was still sitting on the bed, eyes wide at her sudden departure following their little heart-to-heart. "You okay?"

Cass stood and kicked the door to the closet gently shut behind her. In her arms she held a large box of salt and a roll of clear packing tape.

"Honestly? No. I don't know exactly when the next seal is going to break, but I'm going to be jumping at noises until it's done." She stopped at the edge of the bed, eyeing the layout of the room. "Help me move the bed away from the wall, would you?"

Sam obeyed, though he still looked confused. He watched curiously as, once the bed was away from the wall, Cass sprinkled a thick line of salt in a wide circle around the bed and began yanking off strips of tape to secure the stuff down.

"You're… taping down salt?"

"I don't want it to get blown away," Cass said gravely, pressing down a piece of tape carefully to ensure the seal was secure before moving on to the next section. "These aren't ordinary ghosts we're talking about, here. They're…" Cass hesitated, trying to figure out how to phrase it. "Evil murder ghosts of the Apocalypse."

"Most of the ghosts we deal with are 'murder ghosts'," Sam pointed out sensibly.

Cass huffed and glared at him from her spot on the floor. "Yeah, well, I've never even seen a ghost, and I really don't want to get killed by one. I'm not gonna put salt around my bed just for them to blow it all away with their spooky ghost wind."

"Spooky ghost wind," Sam repeated. The corners of his lips were twitching.

"If you're going to make fun of me, you can just leave," Cass griped, ripping off more tape. "We'll see who's laughing when my ring of salt is safe and sound, and yours is blown out the window."

"Sorry," Sam said, though he'd stopped trying to hide the expression and was now smiling openly. Still, he knelt down on the ground and held out a hand. "Here. Let me help."

Cass eyed him suspiciously, but handed him a few strips of tape anyway. He took them and began fastidiously securing the salt line.

"It's just…" Sam paused, seeming to think about how he wanted to phrase his next thought. "You know so much about this stuff. It's easy to forget you're not actually a hunter."

"I've never been a fighter," Cass said, matter-of-fact. "I don't have the heart for it. It's why I didn't try to become a field agent with the FBI—I didn't want to have to serve warrants. I hated the thought that I might have to shoot somebody."

"If it makes you feel any better, the ghosts are already dead." Cass raised her head to shoot him a look that conveyed that that did not, in fact, make her feel any better. Sam's smile widened at the withering look and he said, "Besides. You had enough heart to bust me out of Hell."

"That wasn't me." She yanked off another strip of tape with force. "It was Castiel."

"You stood up to Uriel without him," Sam countered.

"Uriel wasn't allowed to hurt me," Cass said, then looked down at the dark blood stain on her shirtsleeve. "Though I suppose he didn't let that stop him."

"You didn't know that before," Sam pressed. "When they first arrived. You said it yourself, the angels would've tortured you for what you're doing, if they could. But you did it anyway."

Cass sighed and looked up, frowning. "What are you trying to say, Sam?"

"I'm just saying…" Sam shook his head. "You've got more heart than you think."

He gestured for some more tape, and Cass handed it to him silently. She was still mulling over his words as they slowly rounded the circle towards each other. His response hadn't clarified much. More heart than she thought? What was that even supposed to mean? Was he trying to say that she should be more courageous? Or that she already was, and wasn't giving herself enough credit?

She decided it didn't really matter, and decided to chalk it up to whatever mix of guilt and gratitude Sam was currently feeling about breaking the first seal and being pulled out of Hell. Cass laid down the final piece of tape, ensuring the salt line couldn't be disturbed with anything less than deliberate tampering, and sat back, feeling marginally more in control. Ghosts might be coming, but at least they wouldn't be able to murder her in her sleep.

"Anywhere else you wanna lay down a permanent circle?"

Cass squinted at Sam suspiciously, trying to tell if he was being serious. "Are you just humoring me right now?"

"No." He said it too quickly for Cass to believe him, and he quickly added, "Really. I mean, this would never work on a regular hunt—it'd take too much time to tape down the salt—but for our situation now, it's actually not a bad idea."

Cass decided he looked earnest enough. And besides, "We can put one around the fireplace downstairs. We'll need it for the spell to banish the Witnesses."