Right, so I just watched Aliens of London and I wondered what Tosh was doing there. And I just had to write this. Attack of the plot bunnies

Jack was getting frustrated, Tosh could tell, he'd tried Owen's phone five times now and there was still no response. Part of her was worried, but she knew it was probably another drinking binge to try to cope with the loss of his girlfriend, that part worried too actually. She covered Jack's hand with her own, "I'll go, Jack. I probably know enough to get the information we need, and we haven't got time for Owen to surface again."

He looked at her gratefully; they were running out of time, "Are you sure?" When she nodded and headed for the autopsy room to collect some stuff he went to arrange an ID for her, "Just find out if it's the genuine article and stay safe, something feels wrong, don't ask me what but something's not right."

He handed her an ID card, "What am I looking out for, anything in particular?"

"Sorry, Tosh, I wouldn't know without looking, and I can't go."

"Why not?" Because I have a feeling they'll be there, and they haven't met me yet. I can't explain it properly, but it involves the Doctor, my Doctor, but before me. So if you meet him, he's tall, big ears and talks with a northern accent, calls himself the Doctor, that's all, you can't mention me or Torchwood. That could seriously mess up the timelines and, well, we have enough on our hands."

She nodded her understanding and headed for the door, "UNIT's helicopter should be here to pick Owen up any minute, I'll explain the change of plan when they get here."

"Not to worry, I'll do that, I'm coming to see you off at least." He looked miserable

"You really want to go, don't you?"

"More than anything in the world." He replied honestly, but he managed a smile at least, "Still, hopefully it won't be long before the right one comes along."

"What will you do when he comes?"

"I don't know, but I can't promise I'll stick around. I want you to know that, Tosh. Because one day I may just vanish, and I want someone to know that, if I do, it's because I have to. I can't stay here forever, not when I've seen the universe and everything it has to offer."

"I understand." She said, and she did.