The Doctors Filing Cabinet.

Cross referencing.

The Doctor was bustling around making satisfied 'hmming' noises under the main console. The confusion that had followed his regeneration hadn't lasted long. He'd panicked, she'd panicked, but they'd coped. The Doctor, the chin-doctor, had shown her enough for her to fiddle with the stabilisers. She'd stopped them being flung about the console room and was struggling with some levers when he'd gently pried her away from the controls.

"I remember now." He'd said confidently. "Thank you Clara, if you could just…"

And she'd moved out the way, sat on the stairs and watched him.

He hadn't sent them anywhere. As far as she knew they were still in orbit around Christmas. He'd played with the console for a bit, then had gone underneath to mess with some wires. He was still wondering around in the Chins suit.

It grated a bit. She knew that each new doctor was a different man, and usually tried to get himself out of his predecessors clothes as soon as possible. He was wearing a dead mans clothes. The chin had taken off his bow tie though, so at least she didn't have to watch this new Doctor fiddle with it. That would have hurt too much. She toyed with the scrap of cloth she'd picked up off the floor. Maybe she'd keep it.

"Clara?"

She paused, still a bit unsure about how her name sounded with his new accent. New mouth, lips teeth. New kidneys. That made her smile. That was a very doctor-y thing for him to have said.

She stood, stuffing the bowtie into her pocket.

"Coming. You finished getting reacquainted?"

She came down the stairs to find him sat on the floor next to a pile of wires.

"For now. I was half-way through doing something down here before you called me. Now I can't remember what he was doing."

"I didn't call you Doctor. You called me."

"No. You called me. I was with Handles orbiting Christmas and you called me. Asked me out, dumped me, then invited me to dinner."

"No that was.." Clara paused, biting her lip. "That was him. I called him about Christmas dinner."

"Him, me. Spare me the pronouns. The point is, he was fiddling away down here doing something unnecessary. Then there were 300 years of fixing toys and I can't remember what he was working on."

Clara sat down too, and ran her hand over the pile of wires and sockets and blinking lights.

"But you have his memories don't you? You're the same man with a different face?"

"No. I'm a different man with a different face with the same memories. It's not the same thing."

"You remembered how to fly the Tardis."

"I only forgot for a second. I saw you stabilise her, then go to the lever… it was right there on the tip of my brain anyway. One look at you getting it wrong and I remembered how to do it right. Then everything slotted into place again."

Clara crossed her legs under her, interested despite her grief. "So, you don't remember anything from you previous lives until reminded?"

"No, that would be rubbish."

"Well then."

"It's like," He flapped his hands about searching for a word, and Clara was reminded of the Chin. "There's things that all of my past selves have done. Like fly the Tardis. That's a memory, or set of knowledge, that's very close to the surface. It comes back quickly if not instantly. Then there's stuff that's specific to one doctor. One me. If it's a recent me, I'll remember it quicker should the occasion call those memories to mind. If it's an older me, it can take longer."

He frowned, and Clara watched his face. One arm-flap and she'd taken him to be her Doctor. But he wasn't. For a start, he was taking the time to explain something while sat in one place. Chin would have launched himself from the ground, found a prop or announced he was taking her somewhere which would make it all clear… He wouldn't sit frowning, trying to find the words.

"It's like a filing system." He said eventually. "Tardis operation would be on top of the cabinet, or on the floor in front of it. With things like how to use a knife and fork. I don't file those things because I always need them. The second drawer, or level, or something, would be you."

He looked at her without a smile, deadly earnest. Eyes burning into hers. "You were a huge part of my last life, the last thing those eyes lingered on and the first mine latched on to."

Clara wanted to make a joke, a flippant remark to lift the heavy atmosphere but it caught in her throat. The Doctor was the first to look down.

"You're in the current drawer. The things that are happening now to me in this regeneration. The things I find the most important right now." He scratched at his collar absently. Clara wondered if he missed his bowtie.

"Then each life is a drawer. Filled with folders of friends and foes and likes and dislikes. Remember when you and the last me met that Zygon? The first time I met that species I was in my fourth body. I had to open the fourth doctors drawer, open the file about Zygons, cross-reference with Sarah-Jane and UNIT. To think about the Zygons now, as me right here with you, I have to do that plus open the elevenths drawer and open the Zygon file, cross reference with Amy and Rory and…"

"All that?"

"All that. You do the same thing in a way. But you have an awful lot less memories. Your files might be labelled 'primary school, sub-folder year three, sub-folder before Sally moved away. In day to day life you never have to think about Sally, might even forget about her for years and years. But you have to cross reference with your memories of her if you're going to remember Jo and when you started being her friend instead."

"Okay. So why can't you remember about this wiring?"

He frowned at it. "All I can remember when I look at it is that he was thinking about you. He was making work to keep his mind off you while you were away, and failing miserably. So now I have to deal with the mess. I'm not even sure he knew what he was doing as he did it." He stood suddenly. "I'll just have to leave it and wait for something to go wrong, and fix it then. That's what usually happens."

He held out an arm and Clara took it, pulling herself to her feet.

"I'm going to get changed, would like me to drop you home first? It can take a while."

Clara smiled, remembering the enormous closet she'd helped herself to period costumes in. "I'll wait. I might stick around for a few days, in case your memory needs jogging again."

The Doctor frowned. Or maybe he was just looking at her closely, with those massive eyebrows it was hard to tell. "I don't need looking after Clara, you can go home if you like. I know it can be a bit of a shock, if you need a few days to recuperate…"

"I'm fine Doctor really. I was thinking about being a bit more full time anyway. It's difficult dropping in and out of adventures, having to readjust to lesson plans and essay marking in-between fighting baddies and saving the universe. Maybe this is the perfect time to do it." She took a deep breath. "New you, new way of doing things."

"Clara. You are incorrigible."

"No, I'm impossible. The impossible girl, remember?."

He smiled. "I think I was right about that one."

Clara smiled back. This banter was okay. Maybe it didn't have to be awkward between them."File me under whatever you like. But I'm the boss, and I am starting Monday- Sunday from now on. No more Wednesdays."

"Right, I'll just run along then shall I?"

"That's right. Go change your suit and meet me back here."

The Doctor gave her a funny look, but walked off as per his instructions in the direction of the wardrobe room.

"Doctor." She called. "I said run."

He increased his stride to a trot, and disappeared out of sight.

"Run, you clever boy." She sighed, fingering the bowtie in her pocket. "And remember me."