A/N I have loved - and still love - getting your reviews. ;) Let me know what you think. Hope you enjoy.

(Belated) warning for violence. Also warning for character death, and my sincerest apologies to the Guest who would have liked to be forewarned, they're absolutely right.

Sam wakes up and he thinks: Somebody's going to die today.

The thought flashes through his mind and disappears before he really understood it was there. He shakes his head, forgets he even had that thought, and opens his eyes.

The lab is the same as before, the sun still shining behind the clouds, John and Sherlock on the floor, asleep (probably).

"Sam," says a voice.

Sam turns and is on his feet in an instant. There's some guy sat there leaning against the wall, with a low voice and faded jeans. He looks a hell of a lot like Dean.

"Who are you?" says Sam, eyes flitting around for a potential weapon.

The man frowns. "That's not funny, Sam."

Feeling a drawer handle with his left hand, Sam drags it open and spares a split-second glance at the contents. It's full of empty vials and glass containers. Damn.

"Just answer the question," he says. The next drawer has pliers and scalpels. He shuts it, heading towards the other man, who moves around him so they've switched places.

"Knock it off," the man says.

Sam stretches out an arm to try and find the next drawer without looking away. Shapeshifter? Possibly. It's his best guess. "What are you?"

"You've gotta be kidding me." The guy casts his eyes upward for a second as if searching for divine assistance. "Sam, it's me. Dean."

"Yeah. Right." Sam scoffs. He walks forward, trying to herd the not-Dean away from Sherlock and John. "Nice try and all, but my brother is dead."

This momentarily throws the not-Dean. "What? No, Sam…"

Sam takes a glance at the next drawer he reaches. There are spatulas and a series of knives of varying size. He takes one and wishes he had a gun. Or something silver. His mind is buzzing with the overwhelming thought that this thing must die.

"Sam, listen to me. Something's making you forget. You've gotta believe me. Something wants you to forget about me. You've got to fight it."

"Oh yeah?" Weighing the knife in his hand, holding it behind his back slightly, Sam turns and gives his best disbelieving smirk. "Why should I believe you?"

Not-Dean is using the counter to keep himself upright. He looks fairly alarmed and also annoyed, but Sam's not gonna let that sway him. It's just an illusion, not his brother. And something in his mind is drumming away to the beat of kill him, kill him and he doesn't know why.

"Sam," says not-Dean, shivering violently (a trick, probably, to try and lure Sam into a sense of false security). "Think for a second. How did we – you - end up here? I know you remember, somewhere in that massive brain of yours."

Despite himself, Sam finds his thoughts flicking back to the last few days. It's oddly difficult to focus the memories, like trying to navigate the memory of a dream.

"Stop it," says Sam. He takes a few steps forward with the knife, sending not-Dean back until he's against a small second door that says Fire Escape. "I'm here on a case," he says, but the words ring false.

"What case?" says not-Dean, one hand reaching for the doorhandle. Man, this guy was earnest. Or good at acting.

Sam narrows his eyes. "Why do you care?"

"Sam," says the man, one hand poised on the doorhandle. "Look me in the eye and tell me I'm not your brother."

There's a silence. Sam stares hard at the not-Dean's face. There is a flash of familiarity, something so incontrovertibly Dean-like about the figure. The posture, the tone of voice. For a moment, Sam hesitates.

The pause drags until the other man starts to look hopeful, alarm draining from his face. "Sam-"

"My brother died years ago," says Sam, lifting the knife. "So shut up and tell me what you want or I'll kill you. Understand?"

There's a stirring from the general direction of Sherlock and John, the sound of a stool shifting, but then there's silence again.

Sam advances. "So tell me. What do you want?"

His brother – no, the illusion of his brother – looks stricken, and as Sam moves forward not-Dean wrenches open the door, stumbling backwards into a box-like space with some short steps. "I want you to remember me!"

"Yeah. Okay."

Sam watches as not-Dean realises that he's not falling for it. His eyes widen and he starts to drag himself up the steps with hands out holding the walls for balance.

Apparently it takes much more effort than expected, because his face is pale and covered in a sheen of sweat. Sam feels uneasy.

Something's really weird about this whole thing. If Sam could just stop and think for a second. Nothing makes sense and he's not really sure what he's doing in a hospital at all and he's plagued by the sense that something is very very wrong about this, but these thoughts are overriden by the steady beat of kill him, kill him.

"Why aren't you fighting?" says Sam, partly to himself, as the other man opens a trapdoor, letting a heap of sunlight spill in.

He brushes the thought away and some impulse, some force inside him makes him follow the man up the steps and out the door.

He emerges onto the roof of the hospital. A faint wind brushes his hair in his face. Squinting against the light, he can see he is surrounded by an endless landscape of tall grey buildings just like this one.

Not-Dean walks back a few steps, then staggers and almost falls, as if overcome by a wave of dizziness. "Sam, listen to me."

"Why should I listen to you?" says Sam. "You're a shapeshifter."

His blood is pounding through his head and his ears are ringing with the overwhelming force of the thoughts kill him, kill him, as if the message is being shouted out through a hundred loudspeakers.

"I promise you I'm not a shapeshifter," says not-Dean, walking back as Sam walks forward, closer to the edge. "I don't want to hurt you. I'm your brother, I swear I'm your brother. I'm Dean. Come on, man, you've got to remember me."

Sam says nothing, moving steadily forward with the knife gripped in his hand.

"Come on Sam," says not-Dean. "You're not really gonna attack me."

Still Sam advances.

"Okay. You said you were on a case, right?" There's the sound of traffic three storeys down. Not-Dean glances at the edge.

A pause. "Yeah. So what?"

Not-Dean lurches on the spot, but stays upright. "I bet you can't remember the case. What case is it? You can't remember. Am I right?"

Again, Sam finds himself trying to remember. The case was… they were hunting… no, he was hunting… what?

An apartment, the same city, and the clouds are grey outside, there's a doctor and a detective and Cas and in the kitchen he can hear his-

Nothing. You could hear nobody. There was nobody there.

He could hear his-

"Stop it." His head hurts. He feels unsteady.

"It's okay," says not-Dean. "You're remembering, that's good. Come on, Sam, think. It's making you forget, it's making you do this."

Sam squeezes his eyes tight shut for a moment. "Get out of my head."

"What?"

He opens his eyes. "What are you doing to me?"

Not-Dean looks frustrated. "Nothing! It's not me, Sam. It's this thing, it's the fading. It's made you forget. I'm your brother. Damnit it Sam, I don't want to die. I'm not doing any harm. I'm not a shapeshifter."

"I… I'm thinking." The knife hangs limply from Sam's hand.

Even as he concentrates, his memories are shifting and changing, slipping away from his grasp so forcefully it's almost a physical pain.

There was nobody in the kitchen.

He takes a step back and puts a hand to his head, resisting closing his eyes against the ache. "What the hell…?"

"Sam? You alright?" not-Dean (just Dean) frowns.

Letting out a long breath, Sam stands. "Yeah. Dean…"

"Yeah?" The other man looks hopeful.

"I… oh God. I remember now…. I'm sorry…. I remember you."

Not-Dean smiles, properly smiles, and takes some swaying steps forward towards Sam. Sam feels an inexplicable lump in his throat.

They're about a metre apart when Sam lunges. Not-Dean's eyes widen at the unexpected attack and he dodges to the side, and then they're fighting, wrestling each other to the ground.

And he fights a hell of a lot like Dean did, even if the man's unexplained weakness makes the struggle fairly short-lived. By the end, not-Dean is hardly standing on his own two feet.

Sam breaks out of a weak hold and grabs the not-Dean by the collar. They're perilously close to the edge and their faces are very close. Sam can see the bags under the guy's eyes and the sweat on his forehead.

"Sam," says not-Dean, desperately. His voice is hoarse from the exertion. "Sammy…"

"Nice try, but I think I'd know my own brother," says Sam with ultimate disdain. He brings the knife up and stabs the man in the chest with as much force as he can.

He lets go of the man's collar and takes a step back, breathing heavily. Dean's knees buckle and he collapses to the ground. The knife wasn't long enough to reach his heart, Sam judges.

Reaching down, Sam pulls the knife out of the man's chest and stabs him again in the stomach. No use making his death longer and more painful than it has to be, even if it's only a shapeshifter.

The relentless beating rhythm of kill him is gone, leaving only dull silence.

Dean gasps a couple of times, hand reaching out in the general direction of Sam, and then it falls limp on the ground. Blood is spilling from his stomach in an endless cascade. His eyes gain and lose focus, moving from Sam to the sky, unseeing.

He is still.

And that's when Sam remembers.

Dean the Impala hunting the Apocalypse Castiel the fading it's called the fading I'm not gonna fade Sam. It's like waking from a dream, except much more sudden and blinding and a hundred times worse.

A thousand times worse.

"No…" says Sam. His mind is buzzing with the enormity of it. He doesn't hear the traffic or the sound of the door to the roof being opened with a slam behind him, doesn't hear anything except his own harsh breathing as he falls beside Dean. "No."

The knife clatters onto the ground.

"Oh, god, no. Dean…" All of a sudden his hands are shaking like he's in an arctic tundra. "Dean, you were right, you were right, I believe you. Dean. Dean. Come on, man, this isn't funny."

"Sam? What – what's going on?" It's John, sounding healthier and stronger than he has in weeks. The paleness is gone from his face. Somewhere in the back of his mind, Sam recognises why this is, and refuses to accept it. Dean's not gone.

"Dean," says Sam. "Dean."

"Oh my god," John's saying. He kneels down beside Dean and takes his wrist, checking for a pulse. "Oh god. Sam?"

Sam doesn't reply. He stares at Dean and then at John. Dean wake up come on Dean I remember you now you were right okay what do I have to do god damnit.

"Sam, who did this?"

It feels like he's suffocating. John's voice comes from a long way away. At the same time, he finds himself startlingly aware. He takes a deep breath. "I did."

There are more footsteps from behind him, much more faltering and slow.

"What do you mean?" says John. "Why? What – why?"

Long moments pass. "I… I forgot him."

"Oh God. Oh. Oh God, no."

All at once Sam is taken by a wave of pure fury. His brother is dead and this guy, this John, has the gall to act upset and reproving as if he understands. As if it's not his fault. If John had never existed, this wouldn't have happened.

He has never hated anybody so much in his life.

His shoulders tense and he grabs the knife again, ignoring the shudder that goes through him at the thought of what he used it for.

John must have sensed the change, because he glances up and stands quickly. There's not far for him to back away before he reaches the edge.

"Sam," he says. "Put the knife down."

Sam can't fight the lump choking his throat. "Bring him back."

"I can't." John heaves a sigh. He looks sympathetic. "I'm sorry."

"If you die, it will bring him back."

The logic seems irrefutable, and even if it isn't, Sam doesn't care. He's choking up so much he can hardly see. He's sick to his stomach with the thought of death.

"Sam, listen to me, you're in shock," says John. "That won't work. I'm sorry. Truly. I'm so sorry."

"It will," says Sam, though he knows it won't. "It's got to."

There are the footsteps again, nearer. John casts a glance to the side and his expression changes. "Sherlock!"

The detective is forcing himself forward towards them, step by step, each movement causing apparent pain as his face screws up. Tendrils of his hair are lifted by the breeze.

"Get away from him," Sherlock says to Sam, though his angry stare misses and ends up directed at air to the left of Sam.

"Sherlock, get back inside. What are you doing?" Even on the edge, John can't help but slip into Doctor Mode.

Sherlock goes closer and closer to the side of the building, and to John.

"I'm going to fly," he says matter-of-factually. "You should know I know everything."

"Oh god," says John. He turns his gaze back to Sam with renewed desperation. "Sam. Please. I'm sorry. I want to help. But this won't work."

"Why not?" Sam practically shouts, his voice carried by the wind. "Why won't it work? Give me one good reason why I shouldn't try everything I can to save my brother?"

"Sam-" John pauses and licks his lips.

"What?"

"Your brother's gone. I'm all that's left now. He was me and I was him, alright?"

Sam ignores the tears streaming down his face. "Don't. You're not Dean. This is wrong."

Beside him, Sherlock is stepping up onto the ledge at the side, observing the city with utmost nonchalance.

"Sherlock," says John, unable to look away from Sam and his bloodstained knife. "What are you doing?"

"Waiting."

"For what?" John's voice breaks. "Get down, Sherlock. Don't do this."

"I don't think I can," says the consulting detective.

Chancing it, John looks away from Sam just as the detective sways forward. The doctor reaches out an arm and grabs the back of his shirt. "Sherlock!" He turns to Sam. "Please. Help me."

"Why?" says Sam dully. "If I save him I'll just have killed Castiel as well."

"Don't worry, John," says Sherlock. "I'll just fly, you know."

"Sherlock." John's voice breaks. As the detective leans dangerously forward again he grabs his arm, putting one leg up on the ledge to steady himself. "You're ill. Listen to yourself. You can't fly, you won't fly. Please get down. It wants you to die. This time thing, whatever it is, is making you do this. You know that, I know you know that."

"It all makes sense," Sherlock continues. "Rather brilliant, really."

Sam stands, knife hanging by his side, frozen in indecision and numbness and unable to take in what's happening. His mind reverbrates with Dean.

"God, no. Sherlock, no. This is crazy." John's grip on his arm gets reversed as the detective lurches forward and fights to get out of the doctor's hold, dragging John up onto the ledge. Now he's holding John's arm for all it's worth and John can't seem to let go.

"Sherlock! Stop, stop! Just stop! You don't have to do this. I know you don't really want this. This isn't you. Just get down and we'll deal with this."

"I don't seem to be able to do that." His voice drops to a broken whisper suddenly, different from everything else he's said. Somewhere in there, Sherlock is fighting this, and losing. He stares out at the London panorama. "Are you afraid, John?"

"Yes."

"You shouldn't be. I'd catch you, you know. I would always catch you."

"This will kill you, Sherlock. Please, for the love of God, I am begging you, don't do this. Just listen to yourself, would you? Fight this!" He tugs at Sherlock, trying to step down from the ledge and bring the other man with him, but he's held in place by the man's grip and any fierce attempt to escape leads to Sherlock pulling against him in the opposite direction.

"Sherlock," John continues. "This is what it wants you to do. You know that. It's compelling you! You don't have to do this. This isn't you, god, this isn't you. The Sherlock I know wouldn't do this."

"I'm not the Sherlock you know," he says. "I'm much more."

"Please."

For the first time, the other man seems to hesitate. His eyes lose their glazed look for an instant. "John?"

"Yes, it's me, I'm here. I'll help you."

Sherlock lips his lips. "John, for once in my life I believe I'm afraid."

The doctor sags slightly. "Okay. It's okay. Just step down and we'll deal with it. I promise you, it's okay. Just step down, alright? It's just one step."

But the moment's gone. "No, I don't think so. I can fly, you know."

"Come on. Please." He glances at Sam with wide desperate eyes, helpessly trying to drag Sherlock down by pure force without unbalancing him the wrong way. Help me.

"I'll catch you, don't worry," says Sherlock.

Sam looks back at him, and it feels like this is all happening at a hundred removes. He is a distant observer, unable to move or intervene.

"I don't think you understand, John." Sherlock's curls get brushed off his face by the wind. "I'll fly."

"Please. Sherlock, don't do this. You won't fly. Please don't do this. Don't. God, please, don't-"

The detective tilts forward further and further, shutting his eyes, and John is hauled forward with him until they both tumble off the ledge, inelegantly, limbs hitting the concrete and then they disappear over the edge. They fall down past the windows and the Georgian architecture and land in a motionless heap in the street below.

Sam doesn't move.

"John," he says stupidly. "John. Sherlock."

He takes a step forward but the world leans to one side alarmingly, every detail deafening him. The sky is too big and the wind too cold and the city is too loud and endless.

"Dean." The word is a bullet. "Dean, they fell."

He thinks maybe Dean's alive maybe he survived maybe it worked.

"Dean?" He turns to where Dean's body was lying prone and surrounded by blood, and finds nothing. There's nothing there, not even the bloodstains on the stone. Sam is alone on the roof. "Dean?"

No. He can't be gone, he isn't gone. He should be there, he should have been brought back. It wasn't supposed to happen this way.

His legs propel him to where Dean was, searching for evidence that his brother was there. There has to be something. Anything.

There's a cool rush of air and a faint rustle. "Sam."

"Castiel," Sam croaks. The angel, like John was, is restored to his normal state and no longer looks like he's been in a war. "Where's Dean?"

"He faded." The angel wavers but his gaze is hard and searches Sam for a long instant. "You killed him."

"No, you're wrong," Sam tells him. He steps away from the angel, casting around as if he will see Dean's gun lying there, anything to prove that his brother even existed. "You're wrong. He was here. Alive."

He expects the wrath of Heaven to descend upon him, but Castiel is almost calm, though his eyes are sorrowful. "Sam. I'm sorry."

"So get his soul!" says Sam. "Get his soul and put him back."

"I can't."

"Why the hell not?"

"He has been erased. He has faded. He doesn't exist in any form now. Only in your memories. Eventually you will lose those too."

"No," says Sam. "I won't. You're lying. You're lying to me, Cas. You're not even here. This is all a mind game, right? That's what this is. You shouldn't be here, I saw you burning."

The angel doesn't reply. Sam is aware, distantly, that he sounds crazy.

Around them the world is darkening, the light dying faster than a natural evening, the sky misting over black and cold.

"What's happening?" he says, without really caring.

The angel doesn't look away from Sam as he is steadily cast into darkness. "Time is setting itself back to how it should be. The timeline is fixed."

Sam shakes his head. Nothing's fixed. Can't they see that it's all broken?

"No, you're lying. This doesn't make sense." He swipes at the wetness on his cheeks roughly, forces himself to think through the numbing shock. "You…you said that the timeline needed an Arthur. Dean was the replacement. You said all this happened because he was needed."

"Yes."

"So he can't be dead!"

Castiel sighs. "It was a paradox. The universe needed the soul of Dean – or John – so as to save the timeline. It was only in trouble because of the duplicate soul."

A pause.

"Is any of that true, Cas?" says Sam in a low quiet voice. It hurts to think. "Did Merlin and Arthur even have anything to do with it at all?"

Castiel is silent.

"A paradox-" Sam is choking on his own words. "That doesn't even make sense. Bring him back, Castiel! I don't care what it takes. Just find him!"

"I'm sorry, Sam, but there was never any Dean at all."

"No." Sam turns away, shoves his hands in his pockets, with a vague thought of getting his phone. He'd call Bobby, he'd sort this out, he'd find Dean. He finds a piece of crumpled paper in his pocket.

Unfolding it, he sees Dean's scrawled handwriting and his heart misses a beat.

It says:

Hope.

Sam gives a pained moan, screwing the paper up in his hand. He throws it to the ground and heads for the door, determined to find something in the lab, or something in the apartment. Something to prove that Dean was here.

(Unaware that already knowledge of Dean is already slipping away. Unaware that in his mind, his brother is being erased, memory by memory.)

The note gets picked up by a breeze and rolls to the edge, is swept upwards, and is gone.

THE END