Summary: AU What if Mary hadn't been destroyed after getting rid of the poltergeist? What if she was still there? When Mary informs the boys about the possibility of them having a little sister, both brothers set off to find her. Supernatural/Who crossover. 10/Rose pairing

In Supernatural it is set in series 1 of Supernatural during the episode 'Home', Mary attacks the poltergeist that was controlling Sam but this time Mary doesn't get destroyed, she is still there and talks with her boys.

In Doctor Who it is set after the episode The Idiot's Lantern in series 2.

Let me know what you guys think. I am hoping I have both brothers in character.

Some dialogues are borrowed from Home but they are a bit altered.

For this story you guys really need to both watch Supernatural and Doctor Who otherwise some things just won't make sense. Enjoy, read it and please let me know if you guys like it or not.

Prologue

Both Dean and Sam looked at their mother. Dean's eyes were filled with unshed tears as he saw her, looking the same as she had all those years ago when she put him to bed for the last time. She had the same kind smile on her face and she was staring at him adoringly. Sam looked at the ghostly figure of his mother in utter bafflement. He didn't have any memory of her at all but he had slept with her picture in his childhood, she looked exactly as she did in the pictures and he could not believe she was standing there. Sam smiled weakly at her sight, tremulous.

But their mother's smile vanished and sorrow filled her eyes as she trained them onto Sam.

"I am sorry..." Mary whispered sadly for her young son.

"For what?" asked Sam utterly confused. The first thing his mother ever tells her and its an apology? Why was his mother apologising him? Sorry about dad? Sorry about her death? Why sorry?

Mary walked away from her sons and then looked up towards the ceiling angrily.

"Let go of my son!" Mary shouted angrily at the poltergeist who had invaded her home and was hurting her sons.

Immediately the fire engulfs her again. Dean immediately closes his eyes because to see her consumed by fire reminds him of the night of the fire. The fire reached towards the ceiling and then disappeared. Sam felt the presence of the poltergeist disappear and he fell on the floor immediately. Bewildered Sam walked over to where Dean was standing.

Dean was staring towards the ceiling.

"Now it's over" Sam said it, he couldn't feel the poltergeist's presence anymore.

Dean still did not look away, he was staring at the spot he had seen his mother disappear to.

"Mom..." he whispered, wondering if she was still here.

Suddenly the fire swirled in front of them and when it faded away infront of them stood Mary Winchester again.

She smiled at them again this time. Sam laughed in relief, when he hadn't felt anything he thought that along with the poltergeist his mother's ghost had been destroyed as well. At Sam's sudden laughter Dean turned to look at Sam incredulously. Once Sam calmed down he looked at Mary in confusion.

"Why did you say you were sorry?" asked Sam not understanding why she had apologized.

Mary turned her gaze from her eldest son to look at Sam.

"For what that has already happened and for a lot to come," she said it sadly.

Her cryptic words confused even Dean and Sam but before Sam could question her Mary spoke up.

"I cannot believe it, you both are home. I didn't think I would ever see you again," Mary walked towards them now and looked at both Dean and Sam, taking in their features reverently. She raised her hand and touched Dean's hair at which he blinked in disbelief again.

Sam couldn't hold the tears any more and openly cried.

"You mean to tell me that you have been here the whole time?" Sam said it incredulously, shocked at the prospect that all this time she had been here, in their house. If only he had known then he would have visited years ago, he had no doubt that even Dean would have ran all the way here if they had known their mother was here, even if she was a ghost.

"I couldn't leave, especially when I found out something that I needed to tell you. I tried to leave the house to find you boys but I am bound to the house," Mary smiled sadly at that. The fact that she had died hurt her but when she realized she was bound to her house she felt heartbroken because she didn't know where her family was. So she had been over the moon when she saw her boys today. She had recognized them instantly and it broke her heart that she couldn't be there for them in their childhood. But she had to tell them this, they needed to know. John and she had initially hidden this from Sam and Dean had forgotten but now that she could feel her she knew she had to tell them.

"I need to tell you something, it's important," said Mary urgently.

"Then tell us, we are here," said Dean looking at her, confused but none the less willing to listen to whatever she was going to say. She could say she sold their souls to the devil right now and Dean honestly wouldn't care because she was right in front of him. The image of the burning house, knowing his mother was inside it, ate him and now that she was talking to him and was standing right in front of him, it made him happy. Nothing could ruin that. It only made him wish his father was here. Because he knew his father was hell bent on revenge and to meet Mary once again would help him.

"You need to pass along the message to you father as well when you meet up again, because he needs to know this too. We had assumed she died but god she is alive. I know because I can feel her just like I can feel you boys and John," Mary said smiling in relief.

That statement alone confused both Sam and Dean.

"Her? Who is her? And what do you mean you can feel us mom?" questioned Sam.

"I meant I literally can feel you four, you are my family. When I woke up in the house I felt you all and knew you had escaped, that made me happy but it was only then did I feel the fourth presence. I-John and I both assumed that she had died after we couldn't find her but I feel her life like you three. She is alive, well and you both need to find her. Find her before he does and kills her. I have no doubt if he finds her before you then she would die in his arms."

"You mean the demon who killed you? He is going to attack again?" said Dean, uttering the words through his teeth in anger. Their dad wasn't the only one who was angry with revenge. Dean was angry as well, he was angry at the fact that a heartless demon killed his mother but he hid it better than their dad. Sam was a baby, he had no memories but Dean remember everything single detail about his mother and her loss hurt him. The fact that the demon was going to do this to someone else made him seethe inside.

"Wait, wait, wait, who is her? Why is that demon going after this girl as well? It killed-it killed you and Jess but that's related to us, why someone else?" Sam asked sounding confused.

"Who cares why it is going after a girl, we are going there and preventing it. Let dad know as well this way we can be there before it appears and then finish this for once and for all," Dean said it while looking at Sam.

Sam looked at Dean exasperatedly, knowing Dean was currently not thinking rationally because of sudden presence of their mother but before he could reply to Dean, Mary spoke up again.

"Because she is important. You should know about her because she is family."

At that word both Dean and Sam snapped their heads towards her. Dean slowly and warily asked, not sure whether he would like the answer.

"What do you mean family?" Dean asked warily.

"She is your sister"