Sam's been back—really back—for a few months now. When he first came back, he was moody, withdrawn. He didn't say a whole lot, and whenever he did, it was always to Dean. Whenever Castiel showed up, he'd either get really interested in whatever it was he was working on—even if it was just eating his salad—or he would disappear completely. At first, Castiel just chalked it up to post-traumatic stress disorder. Sam had played host to Lucifer. He'd been to Hell. He figured that if anyone deserved a little me-time it was Sam.
But in the past few weeks, Sam's been acting more and more like himself. He's started to sleep again. He's drinking less. He's more likely to take the bait when Dean's trying to get him going. Castiel's even seen him smile a few times and crack a joke or two before he realizes Castiel's in the room. But the minute he notices Castiel is present, he reverts to form, shutting down entirely and refusing to so much as look Castiel in the eye.
Castiel has been trying to convince himself that it's still just the after-effects of 120 years trapped in Lucifer's cage but it's becoming impossible to ignore that Sam is avoiding him. Before Sam went to Hell, nobody was better at knowing what Sam was thinking than Dean. He figures Dean still has a pretty good idea about what's going on with Sam, especially as he's been to Hell before too. So one day when they're alone in the motel room while Sam is out getting the evening meal, he takes a deep breath and asks. "Do you think he's angry with me, Dean?"
Dean manages to look startled, sympathetic and horrified at being asked all at once. He shifts in his chair and Castiel can tell he's trying to decide whether to give an honest answer or make a sarcastic comment and change the subject. "Angry? Why would he be angry with you, Cas? I mean sure, you can be a real dick sometimes but he hasn't exactly been Mother Theresa."
Judging by the fact that Dean has now picked up his father's journal and is thumbing through it, Dean thinks the conversation is over. Sensing his relief, Castiel drops the subject. For the time being.
Things with Sam still aren't any different a few weeks later, so Castiel decides to bring up the topic of Sam again. They're in Bobby's study this time, researching lore on purgatory. He picks up a particularly ancient text and wonders for a moment how exactly Bobby's managed to put together such a definitive library on theology. Even the Vatican has nothing on Bobby's collection.
He takes a deep breath. "I ignored his prayers for over a year, Dean," he says.
Dean slams closed the book he was flipping through. "You ignored mine too and I got over it," he says. He stands up and grabs another text, then walks out of the room.
Castiel watches the doorway through which Dean disappeared for a few minutes before giving up. Clearly Dean has decided the answer he provided was sufficient. Castiel returns to the books.
The next time Castiel decides to talk to Dean, they're alone in the car, checking out a lead on one of the lost pieces of Moses's staff. Castiel figures now is as good a time as any. He has Dean by himself and he can't just disappear or find something else to occupy his attention this time.
Castiel takes a deep breath and begins. "Dean," he says. "The situation with Sam is not improving and I've noticed it's only me he seems to have an issue with."
"We all have issues with you, Cas," Dean says. "It's part of your charm."
Without warning Dean slams on the breaks, pulls the car over to the side of the road and gets out to take a leak.
If he weren't so irritated at Dean's refusal to help him out, he might be impressed by all the ways that Dean has found to say "shut up!" without actually saying a word.
After the last time, Castiel has all but given up on the idea of getting any insight on Sam from Dean. For whatever reason, Dean doesn't want to talk about it and nobody knows better than Castiel that if Dean doesn't want to do something, there is no force on heaven or earth that can make it happen. Instead, he decides to make more of an effort with Sam. The next time he is called to a hunt the boys are working on, he pops into the room right behind Sam. "Sam," he manages to say before he realizes that this was probably not the best strategy. He just barely managed to duck from Sam's swing with a knife. He backs up a few feet, out of Sam's range, before mumbling out a, "I'm sorry, Sam."
Sam sucked in a breath of surprise. "Jesus, Cas! Don't sneak up on me like that!"
"I didn't mean to scare you, Sam. My apologies." He backed up a little further.
Sam sighed. "It's okay. What do you need?"
"I was called. I believe that is me who should be asking that question, Sam."
Sam frowned. "I didn't call you." He paused. "I don't think I did anyway."
"Dean?" he asked, confused, turning to him. "Did you call? I heard prayers, Dean. But they were soft. It was one of you."
"It was Sam." Dean didn't look up from cleaning his gun. "He was moaning for you in his sleep." Sam colored darkly.
Castiel, surprised. turned back to Sam. "Sam? You called me?" he asked, now taking small, careful steps towards him. When Sam didn't attempt to kill him, he moved a little closer as he did with Dean.
Sam swallowed. "Maybe." He mumbled.
"What did you need?" Castiel asked again, more persistently.
"I-"
"Oh for god's sake!" Dean threw up his hands. "Just kiss and make up already!" Something in Sam's eyes seemed to click, and he leaned over, grabbing Castiel by the shoulders and kissed him hungrily.
Castiel, caught off guard, tried to move with Sam, but Sam's all-too hungry lips moved to fast for Castiel to understand. He pulled back. "Sam." he more mumbled than questioned, as though he liked the way it rolled off his tongue. "What was…?" he looked at Sam's lips as if would finish his question.
Sam looked down. "Sorry." He mumbled.
"Do not be sorry. I just don't understand." Castiel explained.
Sam flinched. "Exactly." He mumbled before leaving.
Dean groaned. "Way to go, Cas." He went back to cleaning his gun.
"I don't understand why, Dean. He's been avoiding me for months and now he responds to me in the most particular, intimate, way. Meant for lovers. Does he now think of us as lovers?" Castiel asked.
"Yes!" Dean threw his arms up in the air. "He's been pitterfooting around you because he's nervous and now you just screwed him up more!"
"No one told me this when I asked." Castiel said simply, sitting in a nearby chair.
"Because no one's supposed to!"
"Am I able to fix it?"
Dean sighed. "I don't know."
Castiel frowned. "I'm sure there is a way."
"Go talk with him about it. Not me." Dean growled. Castiel sighed a bit. Not an actual sigh, because angels don't sigh. Simply more air out of his nose than usual. He got off the chair and wandered off in the direction that Sam went.
Sam was leaning against a wall outside, staring at the pop machine to pretend his concentration was on what drink he should get rather than a certain angel.
"Sam, we should really talk." Castiel mumbled.
Sam sighed. "About what, Cas?"
"I really liked what you did, but I don't understand why you ignored me for months then treat me as a lover."
Sam flinched. "It's because I was nervous." He whispered.
Castiel stepped closer to Sam. "Are you nervous now?"
Sam balked. "N-no."
Castiel got closer. "Can I kiss you?" Sam blinked at him before nodding. Castiel kissed him soft, gentle, like a lover would, like a lover should. Not rough, forceful, and hard. Sam gasped and returned the kiss, threading his fingers through Cas's hair. Castiel didn't know what else there was to it, but he liked the taste of Sam. He was sweet and bitter all at the same time. He smelled like the air around them- rain. And Castiel loved it.
Sam broke away and smiled. "Um . . ."
"Yes, Sam?"
"Are you sure about this?"
Castiel thought for a moment "I do believe so."
Sam grinned. "I'm glad you came back, baby."