Author's Note: I know I'm a terrible person, and you really don't need to tell me. So if that's going to be your comment, please save it; I feel terrible enough about writing this already. Blame sharp_teeth, the LJ horror community. It does bad things to my brain. Which was already, honestly, bad enough. I'll also go ahead and repeat that warning that that fic? The one where everyone is happy and well-adjusted and give lots of hugs? This isn't it either.
Dean has to give it credit. It does a good imitation, whatever it is. The eyes, for instance. It has those goddamn puppy dog eyes down perfectly.
But he knows it's not Sam. He knows his brother like the back of his hand, and this isn't Sam. It just isn't. Which does beg the question of where Sam is. "You must think I'm stupid," he says to it. "I know my brother. You're not him."
It makes a soft noise through the gag, not dropping its cover. He could feel sorry for it, almost. If it weren't wearing Sam's face, trying to take his place. Sam could be anywhere now, trapped, hurting (dead). Dean taps the flat of the blade of his bowie against his thigh, and moves forward to yank the gag down.
"Dean," it says, note perfect Sammy-panicked-but-trying-to-hide-it. "It's me. I don't know what's going on, but I swear-"
"Shut up," Dean snarls, bringing the blade against the side of its neck. It cringes and falls silent. It doesn't look angry, though, just afraid. Still pretending. Still faking. "I've known for days you weren't Sam. I just had to be sure. Tell me where he is."
"I'm right here," it says, and Dean moves the knife down and drives just the tip of it into the thing's shoulder. The blade is silver, but the thing doesn't sizzle, just hisses and jerks, trying to pull away. Dean narrows his eyes and crosses a few things off the list.
"Dean," it says, in Sam's voice. Dean stuffs the gag roughly back in its mouth, unable to hear it use Sammy's voice like that again.
When he took it down, it was like it never saw it coming, just expected him to fall for its imitation. Like it thought he'd just be okay with sleeping next to some thing pretending to be his brother every night. But it's been days and nothing from Sam.
It's staring at him again, eyes damp. Dean looks away sharply, because damn, it's too good at that, and yanks the knife roughly out, letting it drag along the thing's collarbone.
The way it screams into the gag makes Dean's stomach twist, because it really does sound like Sam, just like Sam, and that makes every instinct he has clamor to save him from whatever's hurt him, but this isn't Sam, he has to remember that, this isn't Sam.
He glances back after a moment when the scream dies into panting. Its head is dropped onto its chest and he can see the sweat beading on its neck and tears, tears rolling down its cheeks. "You son of a bitch," he snarls. "Son of a fucking bitch. You're going to tell me where Sam is or I will kill you slowly, you hear me?"
He stalks out of the room and dials Bobby's number. "Hey," he says without preamble, "You know of any shapeshifters, things that can take on a human form, that don't react to silver?"
"What?" says Bobby, and Dean grits his teeth and says, "Something's pretending to be Sam. Doesn't react to silver or holy water or anything."
"Shit," says Bobby, "If something's playing Sam, where's…"
"I'll find out," Dean says, lowly. "Just tell me what it is." He hangs up, and goes back to the room. They're in an empty building, condemned, where no one will bother them. The thing's head jerks up when he goes back into the room, and it's already got one arm free.
The anger that flares up is red-hot and wild, and the thing better count itself lucky that he needs it to find Sam and has to settle for breaking its fingers.
He tries taking off the gag again when it stops crying. Its eyes are round and looking at them hurts, but Dean steels himself. It's not Sam. He just has to remember that. "Wanna tell me where my brother is, you fucker?" he says. On Bobby's advice, he's trying a bronze knife this time, resting it just above the thing's knee.
"Dean," it says, "Something's wrong. I don't know what, but you need to talk to Bobby, please, you-"
Dean cuts it off by driving the knife downward, keeping the force carefully measured. He can't kill it. Not until he finds Sam. It cries out, "Dean, stop! Please!" but he makes himself press down harder, no matter how much it makes his chest clench. Monsters never make it easy.
"Where's my brother," he grinds out again.
"It's me," the thing says, panting like it can't get enough air. "It's me, Sam."
Dean jerks the knife out in one swift movement, and it screams. "Wrong answer," he hisses. "I know better. I know. So stop trying to convince me of your bullshit and just-"
It's passed out.
He doesn't know what it is, so he doesn't know what it can tolerate. Dean wraps its knee up after a second and gets a glass of water. Drags up a chair and checks the bonds keeping it in its chair. Still solid.
It comes around before too long, and Dean helps it sip the water and ignores the plaintive, hopeful imitation of Sam's puppy-eyes that it's sending his way. "You're not getting out of here," he says, when the water's gone. "Just tell me."
It licks its lips. Dean rests the bronze knife in sight across his knee and it glances at it with what is plainly fear, even if it didn't seem to show any particular reaction to this knife as opposed to the silver one. "I – don't know," it says, finally. Dean frowns, edges closer.
"What the hell does that mean?"
"I don't know," it says again, and swallows visibly. "Where your brother is." Dean narrows his eyes and stands up.
"You're really starting to piss me off," he says. "How can you not know? You took his fucking place, didn't you? And what the hell are you, anyway?"
The thing pretending to be Sam looks away and seems to be trying to breathe evenly. It doesn't answer for a few minutes, until finally it says, "What did w…what did you and Sam come here to hunt?"
Dean blinks. "Nothing. We weren't hunting anything, just passing through."
"Are you sure?" It says, and Dean is just about to lash out at it again because fuck, this isn't important, all he needs to know is where the hell Sam is when his phone rings. He answers it.
It's Bobby. "Something weird's going on, Dean," he says, right off the bat. "There's no sign of anything like what you're talking about in the area. Last time we talked you were looking for some kind of creature that alters perception."
Dean snorts. "Like what, some kind of LSD demon? Look, Bobby, I just want to focus on whatever the hell this thing is that took Sam. Bronze is a bust too. Did you find anything?"
"No," says Bobby, "But-"
"Then call me when you do," Dean snaps, and hangs up. It's watching him with something like desperation. Dean grits his teeth and thinks not Sam as hard as he can. "Come on," he says, "Let's get some answers."
Whatever it is, it doesn't have supernatural endurance, and it doesn't give up easy. There's blood all over it by now and it still keeps insisting that it doesn't know or, by turns, that Dean's making a mistake. Which he isn't. Dean knows Sam better than anyone, better than himself, and he's not wrong.
It's definitely gotten weaker, though, protests more sluggish, fewer screams. It barely moves now, just flinches, and stares at him with huge wet (Sam) eyes and it just makes him hate it even more, because it's not fair, it's not right, and if Sam isn't okay…
He's gotta be okay. Gotta be somewhere.
"Where's my brother," he asks again, leaving a long score mark along its ribs, and it barely shudders.
"Dean," it rasps, "It's me. Please. Stop. Please. You're killing me."
There's the white hot rage again, flaring up, and he's sick of this, he's so goddamn sick of this, Sam is in trouble and this thing-
It's done before he even realizes it, his knife buried hilt-deep in the thing's gut and it's gasping and looking at him with something like surprise and disbelief, like it really didn't think that he would go through with it, like it really thought-
There's a buzzing in his ears. His phone is ringing, and he picks it up with his free hand, because for some reason he's mesmerized by the knife and the blood rushing out and the way its mouth moves, it's saying Dean, oh god, it hurts, Dean, oh god and Bobby on the phone is yelling into his ear stop whatever you're doing Dean, stop right now and wait until I get there, do you hear me? It's not a shapeshifter, it's not-
The world tilts, jars, stops. And jerks back into motion.
And Bobby's a little late, because Dean's already worked it out.
"So what are we looking at here?" He asks, glancing over at Sam flipping through files. Sam grimaces.
"Not sure. A bunch of people have been killing – spouses, children, girlfriends, and they all say the same thing, that something had taken their place." Sam rubs the side of his face. "There's actually a disease like that, but people don't usually go around killing their loved ones because of it, you know?"
"So what do you think? Possession?"
"No," Sam says, "No, that's not right. It's something else, influencing them somehow. I'm still working on it."
"Dean," says Sam, blood bubbling over his lower lip and dripping to his chin. Dean cradles his face between his hands. He wants, needs to pull out the knife but Sam'll just bleed out faster if he does, and oh god, he's bled so much already, it's all over the floor and Sam and-
-his hands, because he did this, he did this, tortured Sam stabbed Sam is killing – no he'll be okay he'll be fine.
"Easy," Dean says. "Easy, Sam, it's okay," untying the ropes soaked with blood and sweat and throwing them away, pulling Sam gently out of the chair even as he chokes and cries out, trying to curl in around his broken fingers but it hurts too much. "It's okay. I'm here."
"Dean," says Sam, like maybe it'll change if he says it more than once, like Dean won't be the one who did this. "Are you – are you okay," and oh god for a second Dean thinks he's going to throw up because Sam is bleeding out because his older brother is so fucking stupid and he's worried about Dean.
"Just stay quiet," he says, and did he already call 911? He dials again, just in case, and they're going to work out it was him, but that doesn't matter, as long as they fix Sam, they have to fix Sam. "Just stay still. Shh. Come on. You're gonna be okay."
Sam's head is lolling weakly on his shoulders as Dean lifts it onto his legs, smooths Sam's hair back and leaves a smear of blood on his forehead and Sam's breathing stutters, fuck, "Just a little longer," he says, desperately. "Just a little longer-"
"Don't be mad," Sam says, inflating a little bubble of blood with his own breath as he talks. "—at yourself," and yeah, like that's going to happen.
"I don't need to be mad if you'll just be okay," Dean says, and yeah, right, like Sam can help it, like Sam can somehow keep all the blood in his body that Dean so carelessly spilled, right, sure. Sam's eyes drift toward closed and oh god, no, no, no.
"Sam," he says, desperately, "Sammy, come on. Stay with me." He can hear sirens coming, but it's too little, too late, and that's what he's going to have inscribed on his fucking tombstone when he follows Sam down in about five minutes, because his lips are turning blue and his pulse is fading fast and Dean can't do this, can't do this, can't do this.