The Doctor came back down the stairs. "It would require a huge amount of power to transport someone through dimensions" he said before walking off down another set of stairs "follow me," Dean, who was sulking in a corner, because few had ever turned him down, did not follow him until Sam and Clara did. After weaving through the many corridors they arrived in a massive library, multiple stories high. "Wow." Sam said "cool place."

"Yeah," Dean said "You two go geek out" he waved his hand at them.

"So doc what are we looking for" Sam asked.

"Anything that can transport things between dimensions."

"Ah" then, "so none come to mind immediately"

"No" the doctor answered "oh, wait, that was rhetorical"

Sam nodded before seeing a thick encyclopaedia, "should we start here" Sam asked.

"Maybe" The Doctor said "but there are 300 volumes."

"Better get reading, Dean, get over here."

Even with four people it still took them 10 hours to get through 10 books "hold on I think I've found something" It was sam "the arktienes, a highly invasive species that rely almost entirely on technology they can camouflage themselves, teleport and transcend through dimensions."

"Of course, why didn't I think of that?"

"So you know about these?"

"Yes"

"So how do we kill them?"

"That's a very violent attitude."

"Uh-huh" Dean said.

"It's kind of the way we were brought up" Dean said

"And how was that again?" Clara asked.

"How do we kill them?"

"With difficulty" The Doctor answered them "they can camouflage themselves and any one of us could be one, but the problem isn't just killing them we need their technology to get you boys back."

"Right."

"So now you want to talk about the mysterious way you were brought up?" Clara asked.

"No"

"Please"

"Ok" Dean started harshly, "we never stayed in the same place for more than two weeks and we were brought up in cheap motel rooms"

"Why?"

"Because our mother was murdered when I was 5 and Sam was one," then quieter "once you become a hunter it doesn't go away."

"So you guys call yourselves hunters?"

"That's all you got from this?!" Dean yelled in rage. Before storming off down the long rows of books Sam moved to intercept him, but he pushed him off.

He was about to go through the door, when a large armoured man walked into the doorway, no he appeared in the doorway along with another 50 or so around the room. "Oh" said the doctor.