Author's Note: Kate/Osgood femslash. If Osgood became Twelve's new companion, how do they say goodbye? Set after Series Eight, Episode Twelve (pre-broadcast) but no spoilers other than the fact that Kate and Osgood are in it.

She knew what was coming from the moment that she saw the manic look of excitement in his eyes. Most definitely excitement but with a hint of untold danger that frightened her to the very core. His thick, independently expressive eyebrows solidified her fears but she knew there was little she could do about it in the end. Osgood's face had lit up like a child's at Christmas with the promise of Santa Claus, a dusting of snow and the magic wonder of it all. Kate's heart clenched in pain at the realisation that she'd just lost her, to him. The legendary, manic, alien man held out his hand for the younger woman to take.

"Come with me. We can travel the stars, through time and space, together." Osgood grinned widely, honoured to have been chosen by her hero but then hesitated for a moment. She turned to face Kate, a question in her eyes. Kate nodded gently, giving her blessing rather than permission. After all, Osgood was a fully grown woman in her own right, what claim did she have on her besides her own selfish feelings?

"Kate?" Osgood wanted something more tangible than a nod; she needed her girlfriend to tell her it was okay, that the earth would continue to spin on its axis without her.

"Go on, you'll have the time of your life." Kate hoped that she had disguised the tremble in her voice and the gravelly catch of tears that had stuck in her throat.

"You could come with us? Couldn't she Doctor?" Osgood looked back at the silver-haired Doctor who nodded with a rueful grin. He knew that Kate couldn't, wouldn't, leave her hard-earned post as Chief Scientific Officer and Head of UNIT; even in the name of love.

"Someone needs to keep an eye on things here. Besides, I've got to ensure you still have a home to come back to." Kate's voice caught again on the word 'home.' She was wise enough to know that the likelihood of Osgood being returned to her, either in one piece or at the right place and time, was remote. They looked at each other for a few moments; Kate barely holding onto the last vestiges of her composure and Osgood torn between living out her dream and being with the woman she loved.

"Come on Osgood, there's so much to see and do!" Of course the Doctor knew how to ruin a moment but he was probably only trying to help. There was a selfish part of him that always knew he was taking a companion away from friends, family and loved ones to provide company and entertainment for only himself. And even though he had many, many regrets he still couldn't help himself. He got such a thrill at the wide eyed wonder of a new companion stepping through the TARDIS doors for the first time or seeing the birth of a new solar system or a species they had never heard of before. Besides, it was dangerous if he was left to travel alone for too long; far safer if he had a plucky, grounded companion to stop him from going too far. Osgood ran to Kate, slipped an arm around her waist and kissed her swiftly. Kate kissed her back but immediately let her go, otherwise she probably wouldn't have been able to do it all.

"I love you." Another painful twinge shot through Kate's heart at Osgood's words and she had to swallow down a sob.

"Go." It was said encouragingly but for a moment Osgood detected the sadness within Kate's voice. Kate smiled and inclined her head towards the Doctor. "Don't keep him waiting." The younger woman finally nodded and turned towards the Doctor and the awaiting TARDIS. The blue box looked glorious, exciting and inviting and scary all at once. She was finally going to live out her dream and share adventures in time and space with her hero. The Doctor held open the door and allowed Osgood to enter ahead of him. He heard her gasp of wonderment and then the obligatory exclamation of 'it's bigger on the inside…!'

"Inhaler!" Both the Doctor and Kate simultaneously reminded Osgood as soon as they'd heard the accompanying wheeze as she overexcited herself. The Time Lord could no longer look at Kate and headed inside after his newest companion. The TARDIS door shut behind him and Kate stood rooted to the spot as she watched it dematerialise in front of her eyes. She hadn't realised that she'd been crying until McGillop interrupted her aimless staring.

"Ma'am?" She shook herself free of her thoughts and brushed her tear soaked cheeks with the sleeve of her greatcoat.

"The Doctor's gone." It wasn't normally something that would upset his stoic boss as the Doctor had a habit of frequenting UNIT and its officers, especially when there was trouble abound. Or was it that the trouble only started once the Doctor showed up? In any case, McGillop hadn't realised that the infamous Time Lord and his boss were so close.

"I'm not sure I…?"

"Osgood's with him. Travelling. Time and space and…" Her breath hitched in her throat and she couldn't finish the sentence.

"Oh." Not many people knew about Kate's relationship with Osgood but McGillop was intuitive enough to have read between the lines. Had noticed things when others hadn't and heard things that he perhaps ought not to have done. "I'm sorry Ma'am."

"Yeah, me too."