This is an imagined later series, after Ryan, Graham and Yaz have left, but without any reference to how and why. It'll probably get massively contradicted by later episodes, so maybe call it AU?

1.

"Where have you brought us?

Leaning against the TARDIS door frame, the Doctor looked over the garden. It was beautiful, certainly, and peaceful. Graceful trees lined the edge of the neat lawns, with brightly covered flower borders at the foot of the trees.

Behind the garden were rolling fields and green hills, a rural pastoral vision. There was a covered walkway through the garden, intertwined with blooming roses.

Pausing to steady herself, the Doctor regarded her surroundings.

"Thought you'd bring me to a hospital, or a science lab or summat. Still, nice garden. Maybe a bit of peace and quiet'll do me good."

Another burst of errant memories hit and she reeled, clutching the blue door for support.

"Oof, right in the pre-frontal cortex…and a Slitheen memory to boot. Could've been better, could've been worse."

She looked over at the roses.

"I shouldn't spend so long on my own. Think how bad those memories would've been if I hadn't had a friend with me then."

Pulling herself together, she shut the TARDIS door, and strode off down the walkway.

"And think how bad it'll be if you lose any more memories. 'Specially those you actually want to keep."

She brushed her fingertips against the petals of a rose as she passed.

"The whole point of this was to try and get stolen memories back, not lose control over ones you know you have."

Humming gently, she focussed on the surroundings as she walked; the crunch of gravel under her boots, the flashes of sun on her skin, the lazy drone of the insects buzzing around the flowers. The here and now, physical sensations rather than remembered ones. For a little while, it worked.

"Always meant to plant a garden somewhere in the TARDIS. Bit of hydroponics, bit of Zen. Maybe I could get a fishpond?"

But as she came out of the covered walkway, another attack shook her, and the sky turned upside down.

This memory wasn't a nice one, not at all. War, explosions, running but not an adventure. The Doctor didn't want to try and track down what that particular memory was, kept her eyes pressed closed.

"Not now!" she cried. "I can't be dealing with this now!"

"Are you all right? Do you need help?"

A new voice. Young, female by the sound of it, and worried.

The Doctor didn't even realise she'd fallen until she felt hands helping her to sit up, brushing back the hair from her face.

"Are you hurt? Should I get a doctor?"

"I am a Doctor! I'm the Doctor."

She risked opening her eyes. The flashes were fading, the present returning.

The young woman kneeling beside her looked about twenty years old, if you could tell age by appearances, with very long black heir caught in a plait, and her skin gleamed pure gold in the sun.

Her eyes were startlingly blue, and they were looking into the Doctor's with concern.

"OK… but I could call for another Doctor? If you need help?"

"Uhh, maybe? If you could start with where I am?"

"This is the Serenity Garden. In the estate of the Cerebral Order?"

"Ohh!"

Things started to make more sense. The Doctor looked over the other woman's clothes; a kind of tunic in a dusky pink colour with black leggings underneath.

"You're a Sister of the Order?"

"Lay sister."

She helped the Doctor to her feet, dusting her down.

"I don't really have the temperament to be a full sister."

"Fair enough. Lovely idea, the Order, but I couldn't do it either. What's your name?"

"Serene."

"Oh, like the garden?"

"That was the intent. I was a very excitable child, and they named me Serene so that whenever anyone said my name to me, it'd be a reminder that I'm supposed to be calm and composed, not jumping about all over the place."

The Doctor scrunched up her nose at the notion.

"Wouldn't work on me… wait, so you grew up here?"

Serene nodded, guiding them both out of the garden and towards the cluster of enormous sand-coloured buildings, laid out around an open cloister, like an ancient Earth university, all soaring spires and stained glass, a cathedral to learning and knowledge.

"Intergalactic orphan. I was dropped off as a baby, no idea who I am or who my family were. Just a note to look after me and keep me safe. Not a bad place to grow up though; the Order adopted me and let me be a part of them."

It sounded to the Doctor like a carefully rehearsed speech, an answer to a frequently asked question and though she was curious, she didn't push.

Not the time or place for demanding answers from a stranger, not when she herself was dealing with a similar question.

"Where are we going, Serene?"

"Reception. The computers can make an estimation of what help you need and direct you from there. Is it medical help you came here for? A diagnosis?"

"Not really sure. I'm having trouble with my brain, keeps fizzing and bringing up stuff I didn't ask for. Bit confusing, very frustrating."

"You didn't come from the Spaceport, though?"

"My ship doesn't need a landing platform. She's got some very strong ideas of her own. When I started having these problems, she brought me here."

Serene didn't seem bothered by the peculiar answer, but then the Cerebral Order was dedicated to the pursuit of understanding. Possibly she was used to people coming there with odd questions and strange ways.

"Never been here before," the Doctor continued. "Usually I go to the Library if I want to know something I can't find out myself."

Serene's face lit up with a huge smile.

"I've always wanted to go to the Library! I know we have access to almost everything here, hundreds of libraries of our own, but they're all part of the Order. I'd love to go somewhere else, see what it's like there!"

"You've never left here?"

Serene shrugged.

"Can't. No transport, and we don't use money. I earn my keep, but I can't earn anything to pay from passage off the moon."

The Doctor glanced at the sky - moon rather than planet. That was why the atmosphere felt so different. Artificial exosphere, by the feel of it.

"But I can't complain. Things could've been so much worse - what is it?"

The Doctor staggered as another wave of memory rose up violently, cresting within her brain. Pressing one palm to her temple, she squeezed her eyes closed, trying to force it down, but as Serene grabbed her other hand to steady her, something else happened. At first, the Doctor had no idea what, just that there was a shower of sparks, a loud bang (whether real or metaphorical, she couldn't say), and they both fell over.

When she sat up, the memories had stopped exploding, and she felt oddly calm. Serene, however, was kneeling on all fours, head bowed, her fingers digging into the gravel path.

"What- what was that?" she asked, voice shaking.

"Not sure."

The Doctor got up, shaking out her limbs that were no longer fizzing. She couldn't even remember what the memory explosion had been, this time. She looked over at Serene.

"Is your watch meant to be doing that?"

"What?"

Serene sat back on her heels, raising the sparking gadget on her arm in front of her.

"Uh, no. It's a recall device. You know, helps you with study by recording a back up of things you've learned? It doesn't usually look like a firework."

The Doctor pulled out her sonic and scanned both Serene and the recall device, reading through the results quickly.

"Oh. Whoops."

Serene regarded her with suspicion.

"What does that mean? Is it broken?"

"Bit worse than that. See, there's a load of memories that got wiped from my head, and I was trying to see if they were still stored anywhere in my brain. My ship's telepathic, so I thought, maybe she could help? I linked up with her and that's when I sort of… lost control. Everything all whirring around inside my brain, and that's why she brought me here. And when that attack hit just then, and you touched my hand… well, I'm not sure. Are you okay?"

Serene got up, slowly.

"I think so?"

The Doctor made a few adjustments to the sonic and directed it at the recall device. The sparking stopped, and Serene shook it, then pressed a few buttons. A readout display projected above her wrist, and she tapped the tiny silver implant behind her right ear.

"That's weird… says it's full. Didn't think it could get full; it has a compression element that's supposed to reduce everything down for storage."

"Oh."

The Doctor gave her an apologetic look.

"I think it might have, sort of, tried to sync with me. With the memories I was experiencing. Surprised it didn't short out completely, to be honest. Lots of memories, me."

"I.. I have no idea what any of that means. I lost track round about 'my ship is telepathic', to be honest."

The Doctor hesitated.

"Let's go into Reception. See who we can find to help."

"This way."

Serene directed them both through the ornate doors on the front of the building, which was as magnificent inside as it was out. The reception was in fact a vast open space, the full height of the building, with sweeping pillars from floor to ceiling, and enormous stained glass windows to let in the natural light. The Doctor vaguely remembered having once learned that the windows depicted moments of great discovery, scientific and philosophical breakthroughs throughout history. There was an aura of peaceful calm as people went quietly about their business.

To one side there was a white skinned, grey-haired woman in a similar dusky pink tunic, sat behind a desk. Her welcoming smile turned to a frown as she saw who approached.

"Who's this, Serene? I thought you were meditating in the garden."

"I was. This is the Doctor-"

"Hello!" The Doctor interrupted, waving excitedly. The Sister did not reciprocate.

"She's come here for help with her memories," Serene continued. "Probably Professor Leyser?"

"Please place your hand on the print," the sister said to the Doctor, paying no attention to Serene. She indicated the glowing panel on the desk, typing away on her computer as the Doctor complied.

"That's… unusual."

"What?"

"Your print is recorded, but you've never been here before. And your picture…"

The Sister looked between what had popped up on the screen before her and the woman on the other side of the desk.

"Doesn't look much like you?"

"Oh?" The Doctor beamed. "Which face is in your records? Dark hair? White hair? Very short hair? All teeth and curls?"

"Yes. All of those."

"Oooh. Not this face yet, then?"

"No."

"Well, no time like the present to update your records!"

"This is very unusual. But welcome, Doctor. Serene, please take our guest to the diagnosis suite."

This turned out to be down the far end of the reception hall, a series of rooms with various equipment laid out. A blue-skinned young man in a silver tunic set up a machine with electrodes that he attached to the Doctor's temples, connecting numerous monitors.

"You seem to be in good health, generally. Both pulses steady."

"Hard lot to surprise, aren't you? Meet many two-hearted species, do you?"

The Brother smiled.

"We're dedicated to study as much as we are to practise. We see pretty much every species here."

"And you're…Crespallian?"

He nodded, programming a sequence into the electrode machines.

"I've met a lot of species too. Had a sort of friend who was Crespallian. He was a head in a box, last I saw him."

The Brother did not react to that, as serene as a member of the Order was supposed to be.

"There's even a wing connected to the spaceport specifically for those who breathe different atmospheres, or come from planets with other gravities."

"Excellent! What's my diagnosis, then?"

"Memory problems, was it?"

He took out a hand light, shining it into her eyes to test her pupils' response.

"Kind of. I was trying to see if some of the memories that got wiped from my mind were retrievable, and it's all gone a bit wonky."

"Hmm. These readings are a little strange… Professor Leyser is probably your woman. I'll call someone to take you to her lab."

"I'll take her," Serene volunteered. "I know the way."

The Brother, taking off the electrodes, looked over as if he hadn't noticed Serene was even in the room.

"All right. Call for help if you get lost, yeah?"

Serene smiled, seemingly ignoring the implication she couldn't be relied upon.

"I've been roaming these halls since I could walk. I'm sure I can find the way."

She escorted the Doctor out.

"They don't take you too seriously here, do they?" the Doctor asked, watching Serene carefully. The young woman's face wore the same neutral expression as when the Doctor had asked her about her background, and her reply was in the same measured tone.

"Well, they all chose to come here, either to work or to study. I just got taken in like a charity case. Some of them look down on me a bit because they don't think I earned my place, some of the older ones still see me as the grubby child they had to stop running in the corridors, climbing the walls or building forts out of seat cushions."

"No running in corridors?" The Doctor was genuinely shocked. "What do these people do all day?"

"Study. Lecture. Argue."

"And this Professor? You knew she was a memory expert, before we even went near the diagnosis machines."

Serene smiled.

"She keeps lemon drops in her desk. She's been here longer than I have, and she didn't seem to mind being bothered by a curious orphan."

The Doctor smiled back, then she grabbed Serene's hand.

"Run!"

They pelted down the corridor, laughing out loud.

Professor Leyser was a middle-aged black woman with a shaved head, and she wore a blue tunic and a white coat - apparently ubiquitous with scientists across the universe. She seemed genuinely interested in the Doctor's situation, not just as a case to study. Deciding that total honesty was probably the best approach here, the Doctor told the Professor almost the whole story - that she had had huge chunks of her life erased, possibly thousands of years of memories.

"And you don't know which planet you originated from?" The Professor asked, fitting various pieces of equipment onto the Doctor, who was trying to hide her discomfort at experiencing what was so very like being experimented on. She still didn't truly remember Tecteun - her adoptive mother, but also the woman who had used her as a lab rat for possibly millennia - other than what she'd seen in the Matrix on Gallifrey, and she wasn't sure how much to trust what the Master had shown her. She'd managed to resist trying to explore those lost memories for a while, but now she didn't have her friends, her fam…

The Doctor pushed that torrent of confusion and emotion aside, as firmly as possible.

"Serene said you have lemon drops? Love lemon drops."

Professor Leyser, recognising a distraction technique immediately, smiled and indicated to Serene, who began to rummage in the drawers of the desk in the corner of the lab.

"Now, you'll have to concentrate for a while. Tell me about what happened when you tried to recover the memories?"

"Well… my ship has telepathic circuits. We're always in some form of contact, mostly unconscious. Sometimes I can access them a bit more directly, and I thought, maybe if I connect with her, I can try to see if there's any trace of what was taken from me…"

The Doctor trailed off. Serene handed her a lemon drop, then retreated a respectful distance.

"And what happened?"

"I'm not sure. Think I misjudged some of the calculations, and it sort of scrambled my memories. Things keep popping up and I don't seem to be able to control them very well."

"But you're not getting the same attacks now?" Serene pointed out. "When I first saw you, it was so bad you fell down. And it looked like they hurt you."

"You're right," the Doctor realized. "They stopped once your device absorbed some of them."

"There's still an awful lot of activity," Professor Leyser said, reading the monitors from her equipment.

"Your amygdala is lighting up like an aurora. Seems like there's a lot of confusion in your brain about where to store which type of memory, which will probably make it difficult to recall any long term memory at will until we can calm this down. There doesn't appear to be any physical damage, although without accurate mapping of your brain from before…"

The Professor shrugged.

"I should be able to sort this out, but I can't say whether it'll affect your memories. I hope you're not in a hurry to be off because this could take a while."

The Doctor took a deep breath. She could do this. It wasn't prison (again).

"Can't say I'm the biggest fan of tests and being told what to do. But right now, I don't have anything pressing. So…okay."

After a few minutes of setting up further equipment and making complex adjustments, Serene piped up from her place in the corner.

"What's a Pting?"

The Doctor blinked in surprise.

"Why d'you ask?"

"I - don't know. It just popped into my head."

"It's a creature that eats anything inorganic. Nasty little things. Can survive out in space, very dangerous. Have you heard that name before?"

Serene shook her head.

"I don't think so. I don't usually study that sort of thing."

The Doctor thought rapidly.

"What else is there popping into your head right now?"

"Uhh… I don't know. It feels a bit weird."

The Doctor beckoned her over, taking out the sonic and scanning the wrist device once more, before moving up to the partner implant on Serene's neck.

"How does this thing work? Does it literally copy your memories?"

"I have no idea. I never thought to ask, almost everyone here has one, except the visiting academics, they think it's like cheating somehow."

Professor Leyser nodded in agreement, showing her similar device.

"Looks like when you got some memories of mine, they mixed up with yours and now your gadget is trying to sort them out, so they're popping up in your head, rather than mine," the Doctor mused. "Add it to the list. Sure we can sort it out; while you're sorting out my head, you can help Serene with hers?"

The Professor smiled.

"I'll get some more lemon drops."

To Be Continued

Disclaimer: Anything you recognise, probably isn't mine, anything you don't recognise probably is.

Parts of this story have been bouncing around in my brain for years, and I finally got around to putting it all together.

Also, I can't figure out for the life of me how to format this to put line breaks in for new paragraphs, hence the weird lines instead.

Any help would be appreciated!