Small instance of swearing here, don't know if it needs a warning but bear in mind that Dean's going crazy…
Dean caught Sam as he fell to his knees, calling his name, asking him frantically what was wrong-then his little brother looked up blindly and Dean gasped to see the raw and horrified agony blazing in those wide hazel eyes. Even before Sam forced out the words: "It's the wall-" Dean knew what was happening, and panic blasted through him. For an instant he could not move-Dean Winchester, completely paralysed with terror. And then Sam had collapsed in his arms, his body stiff and rigid, eyes staring and filled with pain. "No!" Dean cried. "No, no! Sammy! Sam!" Running footsteps, and then Bobby was dropping beside them, pulling Sam's frozen body away from Dean, shaking him, feeling for a pulse. "It's the wall, isn't it," he said, and without waiting for an answer he was manhandling Dean to his feet, forcing him to help him carry the unresponsive Sam inside. Dean complied numbly, unable to believe that such a thing could have happened. The wall fallen-the wall gone-Sammy fading away-
Last time it had been mere minutes that Sam had lain staring into nothing but his memories of hell, lost in the torment of the past. Dean had almost given up hope then. Now…
He should have expected this. After everything Crowley and Castiel had done to his brother's soul…he should have expected this kind of repercussion. Just as they had thought Sam safe, this stage of the battle at least over…always the same. He could remember so clearly that time over four years ago now, having given everything, fighting so hard to find Sam after he had disappeared, to see him stumbling through the mud in Cold Oak towards them, one injured arm cradled against his chest, smiling that weary, relieved smile Dean had feared he would never see again-then the horror of the inevitable, and the dark shadow of Jake behind him, the crunch as the knife was shoved into Sam's back, his brother's agonised broken gasp as he crumpled-
It was barely different at all. And Dean was sick of it.
Somehow he and Bobby managed to get Sam into the house and lay him on one of the couches in the sitting room; immediately he was flung over his brother, shouting his name, screaming for him to wake up until Bobby dragged him forcefully away and yelled into his face that it would do no good. Dean, almost crying, yelled right back: "How the hell do you know?" And it was then that Sam's condition changed-his body twisted and he gave a kind of strangled gasp, and Dean, startled into hopefulness, turned, desperate. But Sam was not waking. He turned violently, almost falling off the couch, and his head snapped back against its arm as he suddenly screamed, a horrific howl of the most terrible agony. Dean rushed back across to him, grabbing his arms and trying vainly to still him, but Sam was thrashing and flailing wildly on the couch now, his every breath coming shallow and laboured, that horrible animal screaming still coming from his throat in short, desperate bursts.
"Sam!" Dean cried. "Sam, come on, come on! Sammy!" Bobby could only stare in horrified astonishment. This was not just a temporary blip. This was the wall falling, and falling fast and violently. This was every one of the most horrific memories possible overcoming Sam, all at once, destroying him from the inside out. And he and Dean were here to watch it, helpless.
Sam's body suddenly convulsed again, arms striking upwards mechanically, as if not of his own accord, muscles standing out corded and taut. Dean was carding his hair with one hand, trying to calm him, trying to get through to him, but it was hopeless, of course it was hopeless…Sam was unreachable. His screaming was fading now, his voice almost gone, and instead great sobs of breath shook his whole body. His head snapped from side to side with such force Dean was afraid he might break his neck, and now he could hear strangled sounds that might almost have been words: "No-no-no more-please-please!"
"Sam!" Dean cried in despair. And Bobby's voice behind him: "Dean-there's nothing we can do-Dean, it's too late-" But he was not even aware of it. All he knew was that his little brother was lying here before him being invisibly tortured before his eyes, and there was nothing he could do about it, no way to get through to Sam, and it was all his fault, he should never have made that deal with Death, never risked doing this to his baby brother, never let Sam get himself kidnapped, never let him jump into the Pit with Lucifer and Michael in the first place.
And now-could this really be the end?
He had long since given up hoping for a miracle when he heard the wingbeats. He thought, then, that he was imagining things, because why would Castiel be insane enough to return here now? But then he looked up from his despair and saw the grave-faced angel standing there, and he surged to his feet with a cry of fury.
"You goddamn pr*ck, you're gonna pay for this-"
Castiel held up a hand. "I do not come to ask for your forgiveness," he said quietly. "I have come to help."
Dean leapt for his throat, only for the angel to disappear-causing Dean to stumble and crash to the floor right where Castiel had been standing-and reappear across the room beside Sam.
"Get the hell away from him, you-"
"Dean," Castiel said. "I will not stay long. But there is a chance I can help your brother."
"Get away!" Dean roared, and would have leapt again if Bobby had not grabbed him in an armlock and held him back. "Leggo of me, dammit-"
"Let him speak," Bobby said in a voice of deadly calm.
"He did this to Sam!"
"If he's telling the truth then this is our only hope," Bobby pointed out. "Let him speak."
Dean glared back at Castiel. "Make it quick, you traitor," he snarled. "Or trust me I will tear you limb from limb!"
"I have the power of many human souls inside me," Castiel explained seriously. "There is a chance that I can use this power to heal the breach in the wall. But you will have to let me touch Sam's soul once more."
"You are not going near him-"
Bobby interrupted then. "Whose side are you on?" he demanded of Castiel. "Why would you help us now?"
Castiel looked momentarily hopeless. "Because for a very few minutes I still believe that this is the right thing to do."
"As opposed to trying to suck it back outa him five minutes ago?" Dean spat.
"At the time I thought I was right. In a short while I will again. That is what fighting a war does to you, Dean-it makes you conflicted, and it makes you harder." He held up his hands in a gesture of peace. "I do not pretend to call myself your ally any longer. But right now I believe I can help Sam." His gaze strayed to the younger Winchester's trembling, convulsing body. "It may be his only chance."
Dean looked at Castiel, and he felt only hatred, and betrayal, and fury. But then he looked at his little brother's tortured form, and he hesitated. How could he trust Castiel now? How could he trust him to probe Sam's soul again?
And yet what choice did they have?
Sam made another hopeless moaning sound, twisting his head to the side, and Dean decided instantly. "Fine," he snapped. "But I'm warning you, if you double cross us I will personally-"
"Yes, I know," Castiel interrupted almost resignedly, and moved in on Sam. And once again he pushed his hand inside his chest and Dean saw a burst of white light, and Castiel's face furrowed in concentration, and Sam gave the most tortured scream yet, a yell that froze Dean's blood. And then with a bizarre crackling sound, like fire, Castiel stumbled back, the light fading utterly and leaving the room looking duller than ever, leeched free of colour, and Sam shuddered and fell limp and still on the couch, breathing hard as if he had been running for many hours. Dean yanked free of Bobby and half-fell down beside the couch, grabbing his brother's shoulders.
Sam's eyes slid slowly open, dazed and confused, and looked into his big brother's. "Dean?" he whispered. "What…what happened?" And then suddenly his eyes had slipped closed once more and his breathing slowed and he was asleep, exhausted beyond belief by the turmoil of the last few hours. In one involuntary movement he turned his head slightly to lay against his brother, seeking that security even in unconsciousness. Dean, shaking with relief, turned to Castiel, but the angel did not give him time to speak.
"The same rules apply to the wall as before," he said, pale-faced from exertion and grave. "But if I come near him again-"
Dean frowned. "What d'you mean?"
"I mean that I may decide I did wrong," Castiel said. "Protect him from me. There is a part of me that the war has changed, that I can barely control, because it is as much right and a much a part of me as this. If I try later to reverse this-" His face suddenly twisted with a kind of desperate anguish. "Stop me." And then he was gone.
I didn't want to make a false end to the series, incidentally. I just wanted to fill in that gap with my random idea. So that's why I didn't really resolve anything, and thank God tomorrow will bring the next the next episode, yay! But yes, that's why the problem of Crowley isn't resolved and Castiel is only partially redeemed, maybe not at all depending on your opinion…and Sam still has that ticking bomb inside him! So sorry to anyone who expected more, but I didn't have time to make up my own full ending, and I didn't really want to write the end of the season anyway…
So, there, it's finished, just in time! However bad or random it is I'm proud that I wrote it all in four days anyway! I'm so grateful to those of you who reviewed this story and got me writing the end as I planned with your enthusiasm. Thank you!
PS: I promise now I will continue with Personal Demons! Just a temporary break…:-)