The first letter turned up in a PO Box where Dean was picking up a new credit card, three months after their last conversation. Dean had no idea how Sam had gotten the address, but his handwriting was almost painfully familiar, sloping and messy like nothing else about that kid.

He almost threw it away without opening it, but decided there was nothing Sam could say that would matter, not at this point.

Dean,

Hi. I don't know if you'll even ever read this. Maybe you'll just toss it right away.

I wish a lot of things were different. Between us, mostly. But that doesn't matter now. I don't know where I'm going to go now, or what I'm going to do. But I want you to know that you can do this. I know it. I should have known it last year, but I thought…

Never mind. It doesn't matter. Stick with Castiel. You'll need backup.

I'll send you letters every week, to this address.

Sam.

He tossed the letter in his glovebox and didn't look at it twice, but he didn't throw it away. When Castiel returned, he didn't mention the letter.

~.~

Dean,

Just finished off a black dog in Southern Mississippi. I forgot how much I hate Mississippi. The hunt went okay, though. Pretty basic, everything the way I expected it, no surprises. How often does that happen anymore?

Hope you're doing well, wherever you are. Say hi to Cas for me if you feel like it.

Sam.

He was back at the PO box the next week without really meaning to be. It wasn't really all that close to where he'd been, or to where he was going, not that Dean knew where he was going. Castiel's instructions were vague at best and nonexistent most of the time. The angel seemed mostly to attend him for company. Which was nice; just not altogether helpful.

He went back to Bobby's after picking up the second letter, which he read twice, examining it for…he didn't even know what. Something. There was nothing there, though. Just Sam, doing his own thing.

"Sam says hi," he said to Cas on the way to South Dakota. Castiel glanced at him, seeming surprised.

"I'm sorry?"

"He says hi," Dean said, and gestured at the glove box. "He's writing me letters." Castiel frowned at the glove box and didn't reach for them, or answer, or speak for the rest of the drive.

Bobby listened to him tell the whole sorry story and sighed, muttering something uncharitable. "Has he come by?" he asked, uncertain what the vague feeling of mingled dread and hope meant, but Bobby shook his head.

"Nothing," he said. "Not a word. Not even an email."

"Huh," Dean said, and let it go.

~.~

Hey Dean,

Witches, man. You were right about them. I hate them. One gave me a fucking ulcer. It's not going to go away for months. If ever. She went down in the end, though. At least it was only one, not a whole coven. And no demons at all.

I read an article in a St Louis paper about some weird stuff around there. Sounds like the Trickster. Keep your distance.

Hope you're doing well.

Sam.

The third week, Dean couldn't even pretend at coincidence. He'd been driving away from the box when he realized the week was up and turned around to go back for it. Sure enough, there was a postcard, a picture of the Everglades on the front. Dean chuckled. Trust Sam to pick the corniest postcard possible.

Dean thought to wonder why Sam didn't just call instead of sending letters like this, but he thought he already knew the answer. And he was grateful for the letters. Glad to know that Sam was still alive, still kicking, still hunting.

Just because they were apart didn't mean he didn't care at all. It was just better, just easier.

He could manage this.

Dean looked up ulcers, just in case. It sounded nasty, but not lethal. Sam'd be fine.

They would both be fine.

~.~

Dean,

I'm sorry. I'm so sorry. I'm sorry I let you down. I'm sorry I betrayed you. I'm sorry I didn't (illegible scribbling)

There's so much I want to make up to you. I wish we could (illegible scribbling) fix things. I hope you forgive me someday.

Sam.

Dean stared at the letter, scrawled hurriedly on the back of a piece of paper. His stomach turned over. It sounded like a farewell, like a goodbye, and he scrambled for the phone. Bobby had gotten a garbled, unintelligible phone call.

Nothing more than that.

Dean fretted, stressed, and denied both. Castiel was unhelpful, as he couldn't sense Sam at all. Dean spent the week half expecting to get a message on his phone informing him of the death of Mr. Blank at some hospital in Nowhere, United States. The next note came only a few days later, though, and was even shorter.

Dean,

False alarm. Things are fine.

Stay safe.

Sam.

~.~

Dear Dean,

When was the last time we hunted a chupcabra? I remember them being scarier. Was that just me? Huh. Anyway, hunt went well. One shot. I think I'm better at this than I was when I was eleven. Surprise, huh?

How're your hunts going? How's Castiel doing? You know sometimes I try to picture your face as you read these, wonder what your expression would look like. It helps me remember what's important.

Lucifer is talking to me in my dreams.

I think he likes the sound of his own voice a lot.

Sam.

"What does this even mean," Dean demanded of Castiel, waving the letter. "What does he want from me?"

"He does not even know that you are reading," Castiel pointed out. Dean glowered at him.

"You know it's better that way. Safer. Things just end up fucked up when we're around each other. Sam knows that; fuck, it was his idea to separate in the first place." Even if it'd been his to make it permanent. "And now he sends me this – is it true, Cas? Lucifer being in his dreams?"

Castiel shrugged. "It's possible, yes. The sigils would not necessarily protect his unconscious mind."

"What does he want me to do about it?" Dean demanded.

"Nothing, I imagine," Castiel said mildly. "Perhaps he just wanted to tell someone. There is, after all, nothing you can do."

Dean wasn't sure why he felt guilty.

~.~

Dean,

Doing okay this week. Apparently some hunters put the word out, having to step a little carefully. It's okay, though. We had Dad to teach us how to hide, right? Never would have made it this far without all that training. Funny how that works, isn't it.

Managed to pull off a hustle all by myself, though. That's all you.

Hope you and Castiel are still doing well. Haven't heard anything about you; that's probably a good thing, right?

Think I'm going to spend some time trying to work out how to keep Lucifer out of my head. It's kind of annoying. Maybe a dreamcatcher or something like that. He keeps looking like you, or like Jess. I miss her. I miss you.

Take care of yourself.

Sam.

"Hey, Dean," Bobby said roughly. "Heard from some folk looking for your brother. Didn't sound like it was a friendly meeting either. Didn't sound like they'd be too unhappy to find you either."

Dean had Sam's latest letter open on the desk and glanced at it. "I'll keep an eye out."

"No word from Sam," Bobby said after a moment. Dean didn't say anything. Bobby sighed. "Still working with Cas, you idjit?"

"Yeah," said Dean, looking back over his shoulder to see Cas staring at him, unnaturally immobile. "We're still sticking together."

"Good," Bobby said. "At least there's that."

Silence.

"If you hear from Sam, call me," Dean said, finally.

"You could call him yourself," Bobby suggested, and Dean snorted.

"Yeah," he said. "Sure."

~.~

There wasn't a lot in the hunting life that was constant. Even less so now that it was the end of the world. They didn't know where they were going from day to day or week to week, didn't know what they would find, and didn't know how great the disappointment would inevitably be when they did find it.

But he had the letters, Sam's letters, every week. No matter how far he was, he always went back to the box to pick up the letter of the week, and there was always one there.

Dean. Hey Dean. Hi Dean.

They never said much. Sometimes just a couple words. But there was always one there. Sometimes they were worrying. Sometimes they were less so. Lucifer was haunting Sam's dreams. Hunters were hot on his tail. Sam, though, seemed calm, level-headed. And he never asked if they could meet.

Never called.

~.~

Dean,

It's been a year since we separated. Sometimes it seems like so much longer, and sometimes it seems like so much shorter. I've got a little bit of a flu, so I'm staying for a week at a hotel in Austin, Texas. It's hot here, but not too bad. I'm a little tired, I guess.

I've written you a lot of letters. Maybe they're just piling up. I don't know. I guess it doesn't really matter. I can pretend I'm talking to you, and that's what matters. How're you? How's Cas? I wish I could ask for real. Could know. I guess I could always call Bobby.

I wanted you to know that you were right. That we needed to split up. I've ruined a lot, for you especially, and this is so important that…yeah. You were right. I mean, I miss you. But it's for the best. I hope you had a good year, and will have a whole fuckton more.

Goodnight,

Sam.

Dean stared at his phone for a full five minutes, highlight on Sam's number, thinking about calling. He put it away, though. He wasn't done being mad yet, and there were so many important things still to do. They were on the trail of the Colt, and Castiel thought he had a lead.

When things were better, Dean promised himself. When things quieted down a little, he'd send a letter, or leave a message, get in touch somehow. Just to check in. Sam was fine, though. He was just fine, and Dean felt a sudden twinge of resentment that he hadn't been so necessary to Sam after all.

~.~

There wasn't a letter in the mail the next week.

That was fine, Dean told himself. It probably just got lost in the mail. It'd be around.

There wasn't one the next week, either, and Dean felt a chill run down his spine. "What the fuck does he think he's doing?" Dean demanded of Castiel. "He started this thing. Not that I care. It's just stupid letters."

Castiel just looked at him. The angel looked tired, Dean noticed. He had recently informed Dean that he could feel his grace diminishing. He said nothing.

"I don't care," Dean said, vehemently. "I don't give a fuck what he does."

He drove out in a squeal of tires, Castiel motionless beside him, looking for the furthest, hardest hunt he could find on short notice.

Dean came back the next week, though, to find a letter. Just one.

~.~

Roy and Walt are dead.

I killed them. They've been hunting me – us – for a while. They caught up with me in New Mexico. They're both dead. I got out okay.

I thought I was going to die.

If I do – I decided I want you to know. You never did anything wrong. Not with me. Not with Dad. It wasn't your fault, none of this. I wanted you to know that.

Oh yeah. There's also some stuff in a box in Dad's storage unit – the one with the cursed objects – that you might like. Just a couple pictures. Other stuff.

Sam.

Two hunters. Sam had killed two hunters. The writing looked shaky and awkward, and Dean wondered what was going through Sam's head. Whether he was beating himself up about it like he would have once or if he didn't even care.

He called Bobby.

"Word said they weren't killed by anything human," Bobby said wearily. He sounded tired too. This was taking its toll on all of them. "Are you sure…one of my contacts said he'd heard Roy saying the Winchester kid was dead."

"It's Sam's handwriting," Dean said tersely. "Words sound like Sam's. Hard to tell, I guess." He felt his stomach turn over. Just an instinctive reaction. Sam was fine. He'd said so.

They were both fine.

~.~

Hey Dean,

Merry Christmas.

I know, I know. I hope you're celebrating it, though. Wherever you are. With Bobby or Cas or Bobby and Cas. I wonder what Cas would think of that.

It's snowing here. It's not so bad. It could even be pretty.

Freezing to death wouldn't be so bad.

Sorry, that was morbid. I guess I've been thinking a lot about death lately. Sometimes I wonder…yeah, you know. Sometimes I really hope you aren't reading these. Anyway.

I hope you get some pie for the holidays.

Sam.

Bobby dragged him and Castiel in from hunting for the Colt to have Christmas dinner with him. Dean stopped at the PO box along the way and had Castiel read the letter to him. The angel's voice was nearly toneless. "Where do you think he is?" Dean asked, quietly.

The angel shrugged. "I do not know."

Dean imagined, for a moment, Bobby setting some kind of Parent Trap up, with Sam at the house and them driving toward it, but when they got there it was just Bobby and a turkey and some pie. Dean was relieved, really he was.

Bobby gave him the update, even though Dean didn't ask. "No sign of your brother. Not after Roy and Walt went down. Wherever he is, he's hiding but good."

"Uh-huh," Dean said, without interest, and focused on his pie. Bobby looked thinner, he noticed, and older. Cas just looked more jaded. Dean held up his glass of beer and forced a smile. "Merry Christmas, guys."

He dreamed that night of a one-eyed Sam hunting a red-mouthed beast through a snowscape armed with a bow and arrow. For some reason, when he woke up he looked at his phone. It was blinking a message.

1 missed call, it said. Sam Winchester. There was no message.

He rolled over and went back to sleep.

~.~

Hey Dean,

Happy birthday.

Sam.

On January 29th, 2011 Dean got a letter. It had a picture in it; him standing next to Sam, the two of them maybe fifteen and nineteen. Dean had his arm around Sam's shoulders and they were both grinning.

On February 2nd, Bobby died. Demons. They shot him.

"Fuck," Dean said, standing in the living room, just a couple hours too late. "Fuck. Fuck!" Castiel was still, and quiet. He'd been quiet a lot, lately. He said it was getting harder and harder to fly at all. Soon, he said, he would be grounded altogether.

Dean kicked the wall, then kicked it again. For a moment, he almost called Sam. Almost wanted his brother there, next to him.

The moment passed.

~.~

Dean,

I need to know you're still alive. Lucifer tells me things and I don't know – I don't know. I just don't. He's there all the time now and I just get so tired and so

I'm sorry. I'm so sorry. I should call. I tried to call. I'm scared, Dean, fuck, I don't think

Bobby's dead. I heard that. He says he could bring Bobby back. He says he could bring Mom and Dad back. He promises he wouldn't hurt you. Fuck. I don't know. I just don't know. I can't get away, I can't ever get away. I can't sleep and some demons found me and fuck, Dean, I just

I'm not going to call you. I know you're doing a lot. I just want to hear your voice. Just for a second.

I think I'm going crazy.

Dean read the letter three times.

And he called.

The phone rang. And rang. And rang. And rang.

"Fuck you, Sam," he said into the answering machine. "I'm still alive. Don't say yes." He paused. There was more on the tip of his tongue, maybe we should meet up, maybe we should, are you okay. He thought of Ruby and lies and the end of the world, and hung up.

Later. Later, they could meet up again, and there would be time to fix things.

There wasn't a letter the next week. Or the next. The box stayed empty. After almost three years of a letter every week (with one exception), the box stayed empty.

Castiel lost his ability to fly while he was in Alabama and had to take a bus across the country. When he arrived, he drunk all of the liquor that Dean had and fell asleep drunk. And there was no letter from Sam.

Just silence.

And silence.

And silence.

And one night he dreamed of Sam all in white, sitting in a rose garden and spinning one between his fingers. Then he looked up, and smiled.

"Hello, Dean," Lucifer said in his brother's voice.

Dean woke up screaming.