Disclaimer: I do not own Supernatural. If I did, Sam would get a ton more screen time, meaningful relationships with other characters, and Jess. Jess would come back.
But that is neither here nor there, so please, sit back and enjoy!
Dean first notices it in the kitchen. He's chopping up tomatoes for Sam's salad (he's making it without complaint, too, as a show of gratitude to Sam for curing him) and he turns to ask Sam what else he wants on it.
Sam's scanning the room, tracking exit routes, before his gaze hones in on the knife in Dean's hand.
"Sam?"
Sam's gaze flicks up, too sharp and wary, though his voice is level as he asks, "Yeah, what's up?"
Dean clears his throat, off-balanced. "Uh, you want anything else on your salad?"
Sam blinks, his shoulders relaxing slightly. "Do we have blue cheese?"
"… There's mold in the back of the fridge, does that count?"
Sam makes a face. "No, that does not count - wait, we have mold in our fridge?! Dean!"
The next time Dean notices it is on a hunt.
They're cleaning out a vamp nest in Oklahoma, and Dean feels alive like he hasn't in a while, adrenaline pumping and blood flowing, bodies falling in front of him. Sam's at his back -
Actually, Sam's a machine, machete flashing and glistening with blood. No vamp escapes his sight, he's constantly on point, ruthless and efficient in a way Dean hasn't seem him, well, ever.
There's a vamp between the two of them, and Dean reaches it in time to see Sam's machete slice through its neck, his little brother kicking the body away and twirling the machete once, shifting it in his grip back to a ready position.
Sam's eyes are cold and hard and Dean's not entirely sure that Sam recognises him.
"Whoa, easy there, Rambo," he jokes.
Sam rolls his eyes, and Dean feels something inside him relax. He scans the room, tracking the bodies and exit routes (he's been doing that a lot, Dean realises, always keeping an eye for a way out) and wipes his blade clean.
"Burn the bodies out back?"
Dean raises an eyebrow at Sam's brusque voice. "You in a hurry to get somewhere?"
Sam just gives him a flat look, waiting until Dean turns to leave with a huff.
It isn't until they're stopping for gas on the way out of town that Dean realises he never saw Sam's back during the entire hunt.
Weird.
It's funny, but the next hunt they're on, it seems like all Dean sees is Sam's back.
Well, okay, not his back back, but close enough.
There's a lot of interviewing witnesses, and Sam's between Dean and the witnesses every time. It's not overt, but Sam's always positioned so that he can see both Dean and the civilian they're interviewing. And he swears he sees Sam shift into a protective stance when he reaches into his jacket pocket for his notebook.
It's not Dean he's protecting, either.
"Dude, what is your problem?" Dean demands when they're back in the motel room.
Sam's checking for exit routes again, and turns to Dean, nonplussed. "What?"
"You!" Dean repeats, loosening his tie, "You've been off this whole time!"
Sam looks wary now, and his gaze flicks to the door and his gun (what the fuck?) before settling back on Dean, still confused. "What are you talking about, Dean?"
"That," Dean snaps, "Checking for exit routes, always on edge - something I should know about, Sam?"
Sam looks honestly confused. "Dude, in case you forgot, we're hunters. Checking for exit routes when we go somewhere new is what we do so that we don't get dead."
"That's not what I'm talking about and you know it!"
He can see Sam tense, and that too-sharp look is back in his eyes.
"You think I'm gonna blow," Dean realises. "That's what this is, you think I'm going to lose it."
Sam's brow furrows. "Dean, what the Hell?"
"After everything," Dean snarls, "You think I'm going to go out of control and start killing everything in sight, don't you, Sammy?"
Sam's eyes widen. "Dean, that's not -"
"Whatever." Dean turns, heading for the door. "I'm heading out, don't wait up."
The door slams shut behind him, and for the first time in a while, the faded Mark itches on his arm. He needs a drink.
After that, it's like it's all Dean can see.
Dean pulls out his knife to clean, and Sam tenses.
Does it when he pulls his guns out, too. They never clean their guns together anymore, because Sam spends more time watching him like a hawk than focusing on cleaning his own weapons.
Sam never keeps Dean at his back anymore.
And Dean hates it, hates that his little brother won't trust him after everything they've been through. He's always had Sammy's back, through thick and thin, and it goes against the grain of his very being that Sam won't let him anymore.
It fucks up their hunting dynamic, too. Sometimes Sam's fine on his own, completely ruthless and actually a damn good hunter when Dean's occupied. And other times, he's too distracted keeping an eye on Dean to notice the monster about to get a drop on him.
It hasn't gotten either one of them killed yet, but Dean knows it will, and his frustration mounts.
Sam makes sure he's always between Dean and an exit.
Unless there are other people around, in which case Sam makes sure he's between them and Dean.
("I'm fine, Dean, what happened, happened. I'm just glad you're back.")
(Yeah, well it's not like this is the first time Sam's lied to him.)
Everything comes to a head when Dean goes to wake up Sam one morning and turns up loud his music to get him awake.
Sam shoots up with that same cold, hard look in his eyes, gun in his hand, and pulls the trigger.
"Jesus fuck, Sam!"
Sam blinks, his face transforming into an expression of outrage. "What the Hell, Dean?!"
"You shot me!"
(Well, at him, but only because Dean has fucking good reflexes.)
"What the Hell are you doing in my room?!"
"You sleep with a loaded gun under your pillow!"
"Get the fuck out of my room, Dean!"
It's like Sam's a bitchy fourteen-year-old all over again, except Sam has a good twenty pounds on him, and actually can shove him out of his room.
The door slams shut in Dean's face, and, seriously, what the fuck?!
Sam opens the door fifteen minutes later, and nearly jumps out of his skin to see Dean leaning against the wall opposite his room. "Dean!"
Dean lets him stand awkwardly in the doorframe for a few moments before straightening up. "So we gonna talk about this?"
"Talk about what, Dean?"
Dean's mouth curves up in a bitter smile. "Oh, maybe the fact that you just shot me?"
Sam sighs. "Look, I'm sorry about that, Dean. It's, uh, it's been a rough night. Week."
"What rough week?!" Dean demands incredulously, "We've been at home the entire time, taking a break - which was your idea, by the way!"
Sam's hands clench and unclench and he's tensing up right now. "Whatever. I'm gonna go back to sleep."
"With a loaded gun under your pillow? What, are you trying to blow your brains out?!"
Sam's jaw clenches. "The safety's on, Dean."
"You shot me!"
"And you came into my room blaring hard rock!" Sam snapped, "What the Hell did you expect to happen?!"
"Not get a bullet to the face, for one!"
"What do you want me to say, Dean?! Alright, yes, I sleep with a gun under my pillow, because it's the only way I can get to sleep."
Dean remembers Sam's fitful sleep in motels during their hunts and stares.
Sam sighs, getting himself back under control, and he looks worn and haggard. "Can we please not do this right now, Dean?"
Dean steps forward with a scowl. "No, I think we should get this out in the open."
Sam steps back.
His eye widen, deer-in-the-headlights wide.
There's no running away from this now.
Dean takes another step forward and Sam's knuckles turn white around the doorknob to keep himself from bolting and Dean can practically see his pulse fluttering in the vein along his neck.
"What the Hell, Sammy?"
"Dean," Sam replies tensely.
"No," Dean replies, voice hard, "I wanna know, Sam. What the Hell's got you so spooked, you think I'm going to go darkside again? That why you won't let me watch your back, why you try to protect civilians from me, why you look like a jackrabbit staring down the barrel of a hunter's rifle?"
"I don't - I don't know what you're talking about, Dean. I told you, you're my brother and that's what matters."
Dean scoffs. "Yeah. Sure."
Dean raises his hand in a gesture of exasperation and Sam flinches - honest to God flinches.
"Still don't know what I'm talking about, Sammy?"
Dean's voice is flat, and Sam's blood runs cold. "It's nothing, Dean."
"Yeah. So much nothing that my own brother is running around thinking I'm going to try and kill him in his sleep."
"You did!"
Sam looks horrified at the words spilling from his mouth, but he doesn't stop. "You hunted me, Dean! You beat the shit out of me, came after with an axeand the bunker still has friggin' holes in the wall! And the last time you came into my room blaring music ended with you calling our partnership a dictatorship."
"Sammy -"
"And I'm sorry, Dean," Sam continues, his voice fierce and distraught and his eyes overbright with tears, "That I can't just turn it off, okay? I don't know how, and I am doing everything I can. So I'm sorry if this is such an inconvenience for you, but you're just going to have to live with this one."
Sam slams the door shut in his face again, And Dean stares at the Mark on his arm, clenching his fist.
He doesn't know how to fix this.
(He never does.)
A/N: Thoughts? Comments? Concerns? Please, let me know!