Castiel knew that fear could do things to a person. Truly horrible things. It could eat a person from inside out, degrade someone from the outside in, make a person numb to everything around, and shell out everything good until there was nothing left but a husk of who the person once was.

Some could argue that fear had done those things to Dean Winchester.

Sadly, Castiel knew better. He knew it wasn't just fear. Fear, pain, anger, hurt, and loss had been his teachers; and they were cruel.

Dean was still there- still in there. But he had changed. It was this fact more than Castiel's fear, pain, anger, hurt, and loss that made him turn to the drugs and alcohol and women. He witnessed first hand how the love for the one you hold most dear wouldn't always be enough. He knew it wasn't his fault, and he knew there was nothing he could've done.

Oh yes, Dean is the one that Castiel holds most dear. It wasn't exactly a secret, and Castiel didn't exactly try to hide it. Dean didn't exactly not know about it.

...

"Our last night in this world, Cas," Dean had said one night, joining Castiel in his round of drugs, "Our last night. And then..."

And Castiel had looked at him.

Dean just gestured vaguely up at nothing, shifting closer to where Castiel was lying.

"Our last night," Castiel repeated, forever understanding what Dean couldn't say.

Dean closed his eyes and nodded.

"I'll be Velma, you Louise. We'll hold hands and drive off this cliff together," Castiel said with a pained smile.

"Yeah, Cas."

...

Castiel had years to stew in that understanding. Years to sit and watch Dean go through horror after unspeakable horror. And all Castiel could ever do was offer the couch in his cabin for Dean to crash on when he didn't want to feel so alone, yet didn't want to share Castiel's bed.

It was horrible of Castiel to think of it like that, but... Truth of the matter was, it didn't matter. None of it would. Nothing they ever did mattered because no matter what they did, they were always destined to end up there. Dean had always known that Castiel would wait for him until the world ended, and maybe it was because of that that Castiel did have to wait. Maybe if he thought Castiel wouldn't wait, then everything would've been different. But, no. Castiel was willing to do more than that because he was incredibly selfish. The kind of selfish that would make a person wait not only until the end of the world, but for the whole ride there. He stuck with Dean after the apocalypse, Michael, Lucifer, Purgatory, Lilith, Abbadon, Sam, and the virus. He was willing to stick around so at the moment the world ended, he could call Dean his. Even if just once- even if just for a moment. He could call Dean his as much as he has been Dean's.

But then again, maybe that's what has kept Dean holding on for so long.

...

Some days, Castiel wasn't sure if it was amusing or saddening that everyone seemed to know. Only the new girls expected Dean to form a 'connection' with them. All the other girls figured out that both Dean and Castiel were biding their time. No one ever said a word, and no one ever had to. Everyone came around to the realisation sooner or later, and when they did, everyone else would kind of gently grab their arm and shake their head softly.

"No," they would whisper to each other after Dean and would retire to their respective (or each other's) cabins. "Just let them have this. They've lost everything else. Just let them have this."

Chuck was the worst to be honest. Once upon a time he had been inside their heads, after all. Sometimes he would still get headaches, and then he would look at Dean or Castiel with the wrenching pain of knowledge. Sometimes he would cry after those moments.

"I wish you could just be happy," he'd say to Castiel.

And Castiel would know he meant Dean as well.

And then it was their last night on Earth. Past-Dean had come.

That changed everything. Dean was pained just by looking at his future self. Fear hadn't eaten him, degraded him, or numbed him yet. It scared Castiel that he had almost forgotten how Dean looked with hope in his eyes.

Chuck got a headache... Then he kindly distracted Past-Dean.

This was to be their last night on Earth, after all.

And everyone knew.

How they knew was beyond Castiel. Maybe he and Dean were really just that obvious. Point aside, the area around Castiel's cabin was mysteriously clear as he sat down on his couch and patiently waited for Dean to get out of the strategy meeting he called. A second one. Without his past-self.

When Dean came in, he walked to stand in front of Castiel, who was still sitting on his couch.

"Last night on Earth," Dean said.

"It is," Castiel agreed.

Castiel stood up. Dean had lectured him about personal space once. He was clearly uncomfortable now, so Castiel reached up to cup his face very gently- trying to tell him without words that he could bow out.

"You need to be sure, Dean."

Dean put his hand over Castiel's and leaned his cheek into his touch. "It's our last night, Cas. Our last chance."

Castiel brought their foreheads together slowly, still giving Dean time to change his mind. "We could've had it all along," he muttered.

Dean laughed wryly and replied, "I couldn't have forgiven myself."

Castiel was afraid to ask the implications of that statement, so instead he brought their lips together softly. It was barely anything, nevermind a kiss.

Before either he or Dean could push any farther, he led Dean to his bedroom.

He knew he would have to strip the layers that Dean had built up away from him. The numbness, the blind rage, the crushing sorrow, and the multi-dimensional guilt that had built itself into a wall between Dean and the rest of the world. Castiel would strip them away until all that was left was Dean. The Dean that loved pie and Blue Oyster Cult, and watching the people he and Sam saved go back to their normal lives. Castiel just hoped that Dean would let him.

No more numbness after Castiel caressed his face, savouring that Dean was letting him, and softly kissing him down onto the bed. Maybe Dean had to accept slowly that no one was going to pop up and tell him it was wrong. No stern father rose up from Hell, Sam didn't pop up and laugh, God didn't strike him dead.

Castiel allowed Dean to be angry. He went down to his knees willingly, and told Dean that it was okay.

"Let go," he whispered, and Dean did.

Not that Dean wasn't careful; his scalp was sorer than his throat by the end of it. And he thought- almost wistfully- that it was a taste he didn't exactly mind.

He knew it was coming, but Dean started crying after that. He tried to act like he wasn't, so Castiel let him have his dignity, and simply wiped his tears from his face with steady hands.

Castiel settled with his knees on either side of Dean and whispered into his lips, "Can I have you for tonight, Dean?"

Damp eyelashes brushed against his cheek at the question, and Castiel pulled away to look at his face as he answered.

"Yes," he breathed.

Castiel threaded their fingers together as he kissed him once more. Still soft, still chaste.

"Look at me," Castiel said as he pushed into Dean slowly.

And Dean had been tense. He was tense, and maybe a little afraid because everything was stripped away from him now. Somehow, he let this man slowly pry away everything he clutched so tightly for years. It hurt to let it all go, but he knew it would hurt to carry it all again once all of this was over.

Dean almost hated that it took a fallen angel and a last night on earth to allow this to himself. In another time, in another life, in other circumstances, they could've been happy.

Dean told Castiel as much as they laid in bed together, willing the world to leave them in peace for a few moments longer.

"I have been around for a very long time, Dean. I've watched empires rise and fall, I've seen people murder, and I've seen birth. I've been around for thousands of years, but twenty years with you is what it took for me to appreciate true beauty and happiness."

Dean was silent for a moment, watching life stir outside. Everyone was preparing for their suicide mission. He sighed and sat up. Rubbed his eyes. "You calling me beautiful, Cas?"

"Of course I am."

Dean stood up and smiled half-heartedly. "I'm glad I could make you happy."

"Always have," Castiel said as Dean approached the door. "Oh, and Dean."

Dean turned around with his hand on the doorknob.

"Yeah?"

"I love you."

Dean clenched his jaw, looked down, then went out the door quietly.

As Castiel laid back on his pillows and stared up at the ceiling, he thought.

When had everything changed? When had Sam and Dean started drifting apart? What would it have taken to save them?

And he realised why Dean couldn't have forgiven himself.

He gave Dean five minute's head start, then collected himself. He got (re)dressed, grabbed his bag, and headed out the door.

...

Castiel wondered at first why everyone was giggling behind Dean's back. When he saw that Dean was walking in a particularly bow-legged manner, he chuckled to himself, then realised his voice would be tremendously hoarse.

Good, he thought to himself.

"Last night here, then?" Chuck asked from behind him.

Castiel nodded.

He spotted Past-Dean. "I'm riding with him," he told Chuck.

...

"I have a question for you, Dean."

"Yeah?" Past-Dean asked.

Castiel paused as he tried to think of a way to frame the question. How to put it in context so that he could understand everything that transpires between himself and Castiel in the next ten years. A way to phrase it so that it wouldn't sound ridiculous... He soon abandoned the endeavour.

"A favour, actually," he said instead.

"What?" Past-Dean asked.

"If you're offered a chance at happiness, take it. But if for some reason, you can't, then just try to remember I'm willing to wait until the end of the world for you, and I would gladly do it again."

Dean gave him an odd look- like it didn't make sense, but he was sure it would in time.

"Sure," he replied.

"You better remember," Castiel warned, "Because I think that's all that will keep you running for a few years."

Dean nodded once, gravely.

They drove the rest of the way in silence.

...

The Dean from his time and Castiel were the only ones to face Lucifer in Sam's body.

"No matter what choices you make, whatever details you alter, we will always end up... here."

Castiel stepped forward. It was his fault Dean's hand was shaking because it was him that had ruined the barriers he set up meticulously for this moment.

"Sam," he said, "I don't know if you're still in there, but listen to me, please-"

Lucifer laughed, cold mirth in his eyes.

"I'm in love with your brother."

Lucifer stopped laughing, and settled on a general, curious amusement.

"I was lost the moment I touched his soul. It burned with something I had never seen in a man before, and I held it in my hands- no. No I didn't hold it. Nothing could ever hold it because it was desperate to get back to you. The longer I lingered at your sides, I understood why. You and Dean are soulmates. Platonic soulmates, but you love each other with the kind of burning passion that no one but yourselves could understand." Castiel cleared his throat before he continued, "I'm in love with your brother, Sam. Believe me when I say I would do anything for him. I would rebel, I would allow myself to become an enemy to my own brothers and sisters- I would kill my own brothers and sisters... But love is still new to me. For all I know, what Dean and I share doesn't compare."

Lucifer wasn't smiling.

"I love him with every inch of my being, Sam. If there was something I could do to ease his pain, I would. I do what I can. But if there was something I could do to go back in time and stop you and he from meeting somehow, I wouldn't do it. He is better for having met you- for having loved you. That soul I pulled from Hell couldn't have been as beautiful if it hadn't been..." he struggled to find a word, "Blessed for having known you."

Castiel looked at Dean behind him. He looked like he was about to drop the knife he was holding.

He looked at Lucifer, who appeared to be struggling within himself, and then fell to the ground with his hands over his ears.

"STOP!" he bellowed.

"No, listen. Sam, listen," Castiel said, walking over to his head and kneeling by his head, "I'm sorry that it hurts, but listen. I need to thank you because you turned Dean into the man I fell in love with. I'm sorry for everything that has happened between you, and if I could go back and time and stop Dean and I from meeting, knowing that it would save you, I would. There is no one in this world, heaven, or hell that could love your brother like you do, and there is no one that can love you like he can..." Castiel pulled Lucifer's hands from Sam's ears, "And for what it's worth, Sam, I never told you, but I love you too. You were always like a brother to me. If I could have my way, I'd marry Dean and we would be brothers. I never wanted to pull him from you. For making you feel like I was trying, I won't ever forgive myself, but can you forgive me?"

Lucifer stopped struggling in Castiel's hands and went limp for a few seconds. Castiel didn't dare to breathe, Dean didn't move.

Suddenly, Lucifer gasped and bolted up. Dean pulled himself together and put his knife at the ready, but when Lucifer turned to Castiel, it was with Sam's eyes.

"Yeah," he said hoarsely. "Yeah, I can. I'm sorry too."

He promptly passed out.

…

When Sam came around again, Chuck, Dean, and Castiel were looking at him. There were a few others he didn't recognise, but he didn't care because his headache was killing him. He put a hand over his eyes and groaned. He was on a bed of something soft- a little over-warm now that he thought on it.

"Sammy?" Dean's voice asked.

Sam realised he was crying. "I'm sorry, Dean."

….

Dean grabbed the back of Castiel's collar to lean his head back and kissed him, trying to pour all his thanks and apologies for all the years they missed together into it.

Sam would be okay. Lucifer was still in there, but Sam could hold him down. Now he knew once and for all that he would have two people to help him do that.

"How did you know?" Dean asked.

"I didn't," Castiel replied. "I honestly wanted to thank him for the time he gave to us, but then I realised he probably thought he was losing you to me... I would like to believe I understand your bond better than anyone, so I wouldn't ever come between you."

Dean was silent for a good long time. He was sitting cross-legged on the Impala with a beer, and Castiel was leaning against the driver's door. The stars were out, the night was clear, the virus was gone, and everyone was rebuilding- some more than others.

"Can we go someplace quiet, Cas? Can you, me, and Sam go to Sioux Falls and start a life there?"

Castiel looked up at Dean and smiled. "I would have it no other way, Dean."

Dean smirked into the rim of his beer.

"I love you too, Cas."