The first time it starts to happen, Sam doesn't think there's anything that Dean can do about it, anyway so Sam simply doesn't tell Dean that Lucifer's getting stronger. Instead of just a shadowy outline, Sam can see him clearer now; feels like if he reaches out, he can touch him. He's tracing the scar on his hand more and more often, trying to keep him away. It's not really working anymore. Lucifer blinks, but doesn't disappear. He can't get rid of him.

He catches Dean watching him from time to time, eyes worried. But he's been like that since Sioux Falls and since he doesn't actually say anything, Sam figures he's doing a pretty good job of hiding it. Or he was. Until this hunt. They're standing over the grave and Dean has just poured the salt over the body. The ghost is coming at them, and Dean's yelling at him to burn the damn thing but he can't. One second, he's standing next to the grave with Dean and Lucifer's leaning against another grave watching with mild disinterest. Sam's used to that, life with Lucifer observing his every move, offering snide commentary even when he's brushing his teeth. But the next second, Lucifer's beside him, grabbing the lighter out of his hand and tossing it aside. Sam turns to stare at Lucifer who's grinning at him.

"Didn't think you could keep me away for long, did you Sammy?" he asks in that smarmy voice of his that has haunted Sam's sleep since Castiel tore down the wall.

"Sam?" He can hear Dean's voice, sharp with what sounds like exasperation—or maybe that's desperation. It's difficult to tell with Dean—but it's distant. "The lighter? Sammy?"

He shakes his head and rubs his scar, trying to force Lucifer into the background and bring Dean closer but the cut is fully healed now. There is no pain, just a slight ridge in the skin where the shard of glass tore through his hand. There is nothing whatsoever tying him to Dean.

Lucifer doesn't even fade for a second this time and Sam turns to him in horror. Dean's voice, shouting out to him, fades completely. Sam doesn't even feel the heat from the flames as Dean finally picks up the lighter and sets the bones on fire.

"It's not real, Sam," Lucifer says, turning to look at the flames. He waves a hand through them and lifts it for Sam to show that it hasn't burned him. "I only let you believe it was. Makes the torture even better, don't you think? Giving you the hope, then yanking it away? You're so much fun to watch when you think you're back up there. It's almost sad, really."

Sam looks helplessly at Dean but Lucifer's right in his ear now. Sam can't even hear what Dean is saying. "He's in bed with Lisa right now. True…he's having a nightmare about you. But she'll wake him up soon. They'll kiss…cuddle…you know what comes after that, don't you Sam? By the time the morning comes he'll forget all about the dream."

"No," Sam says. "No, you're wrong."

He digs a fingernail into the scar. The sensation is slight, but it's there. For a moment, it's enough. Dean's back again. Dean's talking to him.

"Okay, Sammy," he's saying. "He's back, isn't he? We'll fix this. You and me, right?" Dean's got his hand now and it feels warm, real. Sam can believe for a second that it is. "We're going to figure this out. We figured it out once before. We can do it again."

Sam looks at Lucifer, who's shaking his head. "I can make you believe anything I want you to believe, Sam."

For the moment, Sam chooses to believe Dean. Dean leads him back to the Impala and guides him inside. Once he's in the driver's side, Dean takes Sam's hand again and digs his fingernails in. "You feel that?" he asks.

Sam can't seem to make his mouth work, but he nods. He can feel it. Lucifer's fading. Not much. But enough to anchor him to Dean.

The entire way back to the motel room, Dean doesn't let go of Sam's hand.

"How long?" Dean demands. Sam doesn't really have an answer. Time isn't a real thing to him anymore. He's not sure how much time has passed when he's slipping back and forth. Sometimes, he's surprised to find the entire night has gone by. Other times, what feels like days spent with Lucifer turn out to only be a few minutes.

He shakes his head. "Don't know."

"You cannot keep this from me," Dean says. "Sam, when the lines start blurring you've got to let me know."

Sam stares at Dean. Somewhere at the back of his mind is an angry retort about pots calling kettles black. Sam reaches desperately for that anger but can't quite reach it.

"Go on, answer him," Lucifer says. "He's here right now. Or…I'm letting you believe he's here. You might as well take advantage of it. Have one of your little…brotherly heart-to-hearts that you're so fond of."

Sam stares at Lucifer for a beat. Dean's gaze follows Sam's. Sam wonders if he's even aware of it. "And what are you going to do?" Sam asks. "You can't fight reality."

"A good question," Lucifer agrees.

"Sam!" Dean's voice, slightly panicked, draws Sam back to the little motel room. "You listen to me, you understand? That," he motions in the general direction that Sam has been staring and Sam wonders briefly if Dean can see Lucifer, too. He shakes his head, trying to clear it. "Isn't real. We've talked about this. I'm real. You're real. This world is real and I can not save this shithole alone, okay? You're not done here yet. You don't get to quit like Castiel did, do you hear me? You don't get to leave me."

Castiel…somewhere inside Sam feels a searing pain. He hasn't allowed himself to so much as think about Castiel in the last few months. It was too much. Too hard. But the pain isn't physical. It's more like the pain he felt in Hell, psychological, emotional…when he looks over, Lucifer is now a fully formed figure in the room, as dense, as alive as Dean. Maybe even more so.

"Castiel's not dead," Lucifer tells Sam with a smile, like it's Christmas and he's just given Sam the best present he's ever gotten. He's surprised to feel the faintest flicker of hope at Lucifer's words. "All part of my little game. Give you back everything, then take it all away, piece by piece. First Castiel. Then that damn car of yours that got us locked up down here in the first place. I've saved the best for last, of course. Couldn't decide what would be more fun. To kill him out right…or let you figure out that you were right, all those months ago. You're still in hell, Sam. And I'm going to take Dean away, too. You can't fight it."

Sam doesn't argue this time. Doesn't even try. "What's he saying to you?" Dean's asking. "Sam! Whatever he's saying to you, don't you listen."

Lucifer has stood up and walked over to where Dean is pacing, looking around the motel room as if something in it holds the key to all of this. "He's figuring out what's real," Lucifer whispers. "Figuring out it isn't you, Dean." Then he's beside Sam again. "Your time is up, Sam," he says and raises his fingers to snap them, to snap Dean away.

Sam can't allow that. In a minute. In a minute he'll give in. Won't even try to fight it anymore. But not yet. There's something he needs to say first. Desperate, he reaches out and grabs Dean. The momentary contact centers him again. Lucifer sits back down. "As you wish," he says and he looks bored again. "But don't take too long."

"Maybe it's better this way," Sam says quietly.

Dean stops pacing for a second and whirls around to stare at his brother. "Better? Sam, what the hell are you talking about?"

"If…you're not real. If…this isn't real then," he swallows then takes a deep breath. "Then…Castiel is still alive."

Lucifer nods his head approvingly. "Now you're figuring it out," he says. "That's right Sam. Stop fighting…it's all okay up there. They're all happy up there. You coming back…that's what ruined it all."

"And you…" Sam begins, but his voice isn't working quite right. He stops and takes a deep breath. Dean's kneeling in front of him now, shaking his head, telling Sam to stop. Sam lays a hand on his arm and stares at him. He has to say this. It's important that he finds the right words to make Dean understand. So when Dean wakes up he'll know. He'll know Sam's okay. That he doesn't have to protect him.

"You're still with Lisa and Ben, Dean," Sam says finally. It's more difficult than he thought it would be, but his brother deserves this. Deserves to be with Lisa and Ben and to not have to worry about Sam. "You're still happy. You're not in this stupid motel room in the middle of nowhere covered in grave dirt and trying to fix your broken little brother. Again. If I'm down here, then you're up there, with them and you're happy."

Lucifer smiles. Nods at Sam. "Very good, Sam." He stands up, stretches. Pats Dean on the back. Sam could swear Dean flinches.

"No," Dean says. "No. Sam, none of that is true. If you let yourself get dragged back down there, that doesn't change anything. I'm still not with Lisa and Ben. Castiel wiped their memories, remember? And Cas…Cas is gone, okay? He got dragged under with the Leviathans. He's not coming back just because you let Lucifer take control. None of that changes. Maybe in there, but not out here. And I can't do this, Sam. Not without you. We did not go through all of this just so Lucifer could win in the end, anyway. I swear to you, you go with him…"

Lucifer's sitting forward in his chair now, eyes alight with fascination. "You've gotta love a man who won't quit, don't you?" he says. "I wish he'd have said yes to Michael. That would have been one hell of a fight. He just doesn't give up." Lucifer eyes Sam. "And neither do I."

Sam has lost track of Dean completely now. He wonders briefly if he's gone but then Dean's standing in front of him, grabbing his hand and running his finger roughly over the scar. "Can you feel anything?"

Sam stares at Dean's hand in his. "Can you feel that?" Dean asks again, digging his nail in this time. Sam looks up. Lucifer is as present as ever. This is the first time that Dean's touch on his scar hasn't brought Sam back to the motel room.

Lucifer grins. "Save yourself the heartache, Sam. Quit now."

But Sam can't. Dean hasn't accepted it yet. He'll go. But not until Dean knows he's okay. "No," he says, shaking his head. "No."

He isn't talking to Dean but Dean doesn't seem to realize it. Dean looks around the motel room, grabs a knife out of his duffel bag and begins taking off his belt.

"Dean, it's okay," Sam says.

Dean shoves his belt in Sam's mouth and grabs Sam in a hug. "This is real," Dean says. Sam can feel the warmth of Dean's body against his. He looks at Lucifer. He's faded. Ever so slightly. But enough that Sam is beginning to wonder again. He sinks into Dean.

"The pain? The pain makes it real, right? So all we gotta do is bring back the pain," Dean says, pushing Sam away ever so slightly and taking out a bottle of whiskey. He pours it over the knife. It's a pitiful excuse for sterilizing the knife but Sam appreciates the effort.

"Enough!" Lucifer shouts, raising his fingers once again to snap Dean away. Sam can't let him.

"Look here, Sammy. Don't look at him. Look at me. He's lying to you." Sam digs one hand into Dean's arm and holds out the other, his eyes meeting Dean's.

Without dropping his eyes from Sam's, Dean reaches down and grabs the hand that Sam is holding out with his left hand and with his right, pushes the knife down into it Sam's hand. With the first searing shot of pain, Lucifer flickers. Sam watches the blood curl out from underneath the knife. The pain spreads across his hand, and travels up his arm. Lucifer begins to fade.

"You back with me?" Dean asks. He takes the belt out of Sam's mouth and tosses it aside, searching Sam's eyes.

"This isn't over," Lucifer says.

Sam looks behind Dean, to where Lucifer is leaning against the far wall. He's there. He's always there. But he's nearly transparent again. Sam shivers, suddenly aware of the cool dampness of the dark motel room and the smell of the grave dirt that still clings to both of them. The blood is sticky on his hands and he can again feel the roughness of Dean's calloused hands against his arms. He leans forward and rests his forehead against Dean's shoulder. Dean doesn't push him away.

Sam nods. It's a response to Dean and Lucifer both. Dean hands him a rag and he presses it against the palm of his hand to staunch the bleeding. He knows Lucifer is right. He'll have to fight this battle again. But for now, he's back. He's with Dean. He knows it's real.

And that's enough.

He doesn't have to tell Dean when he's starting to slip, not after that first time. Dean's always watching him, looking for clues that Sam's losing the battle for reality. He keeps a sterilized knife in his bag and checks Sam's hand every day now, gauging the healing. Eventually, he tells Sam, they'll have to find another place to cut. This one will scar over too badly. But for now, he checks Sam's hand every morning. Opens it back up and bandages it when it starts healing too much. And while some part of Sam objects to Dean treating him like he's 5 years old again, Sam knows it isn't fair of him to ask Dean, after all these years, to keep doing it, to keep taking care of him. So mostly he's just grateful that he doesn't have to ask; Dean just does it. Just like he always has. Just like he always will, Sam supposes.

"Ready?" Dean asks.

Sam grips Dean's arm tightly, his fingers digging in as he holds out his hand and looks over Dean's shoulder at Lucifer. Lucifer is glaring back at him in defiance. The pain has become triumph for him now, the one weapon in his arsenal that can beat the devil at his own game. "Ready," he says.