Disclaimer: I do not own Harry Potter or Supernatural.
AU. I have only watched some of S4 and none of S5 but I will briefly use some ideas from that. Obviously set post books for HP but I only read as far as OoTP so AU after that. Will be DeanHarry with Harry one year younger than Dean. Brief slight crossover with Buffy.

Chapter 1

"Sam! Damn it Sammy answer me!" Dean screamed, searching for his brother and trying not to slip in the mud.

"Over here Dean." He turned to see Castiel kneeling nearby and at his feet...

"Sammy." Dean choked, staggering over to collapse at Sam's side. Sam's eyes were wide open as he gasped for air. Dean grabbed his hand and felt Sam weakly try to return the grasp as he looked his baby brother over for wounds. He choked back a sob as he saw the hole through Sam's chest. The wound was fatal, no mortal medicine could heal that but maybe...
"Cas please, help him." He pleaded, looking up into sad blue eyes.

"I cannot heal him Dean. I can ease his passing if you wish but that is all." Castiel answered softly. Once he would have been almost glad for Sam's death due to his tainted blood and his letting Lucifer loose but that had been before he had truly begun to know Samuel Winchester for who and not what he was. He honestly wished he could save the mortal.

"All you have to do is ask." He spun, ready to defend the brothers only to stare in surprise at the woman making her way to them.
"Hello Castiel." She greeted him and Castiel nodded.

"Halkfrek." He greeted warily, Dean was ignoring them, focusing solely on his dying brother and honestly not caring if he died too. He'd done what the angels wanted, Lucifer was gone and now he was losing his brother again only this time there was no deal to make.
"Not here to cause trouble angel, I'm here to help."

"How?" Castiel pressed.

"You were wishing for Sam to be saved and I can do it but you got to say it out loud." Her words finally got Dean's attention.

"How?" Dean asked, looking up as he cradled Sam close.

"Halfrek is a vengeance demon, they answer wishes but there is always a catch." Castiel answered and she nodded.

"Yeah but it won't be that bad. Not even we wanted Him free so consider this a favour for stopping Him." She answered.
"So say it out loud Castiel." The angel stared at her and then down at Sam and Dean before nodding.

"I wish for Sam Winchester to live." Castiel whispered and she smiled.

"Wish granted." With that she vanished and Sam gasped, convulsing in Dean's arm as blood leaked from his mouth. He stared up at Dean and managed a small smile before he went limp, eyes open and unseeing.

"Sam? Sammy!!" Dean screamed, rocking the still body in his arms. Castiel rested a hand on Dean's shoulder and then they watched as Sam's body faded away, leaving only the band he wore around his wrist.

"She couldn't heal him either, it doesn't work like that. Sam had to die for the wish to work. Now you simply have to find him." Castiel told him and Dean frowned, clutching the band.

"I don't understand. Won't Sam just call or something?" Dean asked and Castiel sighed.

"Sam is alive but..."

"But what?" Dean demanded, standing to face the angel.

"I do not know in what form he will be. It is possible he is waiting somewhere, confused for you to find him. But that is unlikely. He will have been changed in some way, he may not even be your brother anymore but he will be alive." Castiel's explanation made Dean freeze. Not his brother?
"I will see what I can learn. If you search for him do not search for his name but his essence, his very soul. Your friend Bobby may know a way. I will return when I know more." With that Dean was alone on the battlefield.

Bobby watched over Dean as the younger hunter poured over his books. Dean had told him what had happened and he was grieving for Sam himself. Even if they found the kid, he wouldn't be their Sam anymore, not if the wish changed him. But that wasn't stopping Dean from searching, he needed to know Sam was okay and that was why Bobby was helping, because Dean had said that he wouldn't approach Sam if the kid was happy in his new life. They both started as Castiel suddenly appeared in the room, Dean scrambling to his feet.

"Cas? Have you found him?" Dean asked and Castiel nodded.

"He is in New York." Castiel answered and Dean sighed in relief.

"Is he okay?" Bobby asked and the angel nodded again.

"But?" Dean pressed.

"He is currently eight weeks old." Castiel stated softly and Dean collapsed back onto the chair, eyes closed.

"His family?" Dean asked and Castiel actually sat down opposite him.

"That is complicated. All I was told is that the person who has him has also saved the world before. But I do not know exactly who or where within the city they are." Castiel explained, leaving out how hard it had been to find even that much.

"Guess I'm going to New York then." Dean stated and Castiel nodded.

"I will take you now and help you search." Castiel said and Dean mustered a smile of gratitude. He looked over at Bobby who smiled and nodded.

"I'm here if you need me kid." With that Castiel, Dean and the Impala vanished.

He stared down at the baby on his bed in confusion. It had not been there when he'd gone into the shower half an hour before. He approached cautiously, scanning for traps but finding none. He reached out and picked up the sleeping baby, smiling as large hazel eyes slowly blinked open and focused on him.

"Hey there kiddo, where'd you come from? Does the stork actually exist, huh?" He asked and the baby gurgled at him.
"Don't suppose you know how you got here?" he asked and then rolled his eyes as he found the letter pinned to the back of the baby's one piece. He pulled it free gently and unfolded it.
"Okay. Guess it's not the oddest thing to ever happen to me hey little Samuel." The baby fussed.
"Sammy? Sam?" The baby settled and he smiled.
"Sam it is then. Don't worry baby, I'll take good care of you, yes I will." He cooed and the baby reached out to clutch his glasses. He laughed but let the baby play with them until hazel eyes locked onto emerald.