Apparently, there was supposed to be more of a backstory for Idris (and Auntie and Uncle), in the episode but there wasn't enough running time. So I wrote my own:

Idris Before

Idris wanted to explore. Always had.

When she was little, that had been fine. She'd had the whole junkyard to explore, and House had indulged her. Auntie and Uncle hadn't cared too much what she did, as long as she didn't get hurt – it wasn't until much later that she'd learned why that was so important.

She didn't remember anything about what or where she'd been before she lived on House, and for a while that didn't matter either. There was always somewhere to explore, something to look at – some of the computers from the ships that came through the Rift still worked, and she'd learnt to read from the subtitled last log entry of the Captain of the StarStrider. He'd been like her first friend, really, as she watched him over and over, deciphering the words beneath him as he spoke. From there, she'd figured out how most of the bits that still had life in them worked, but no-one else seemed to care about that, not even House. He liked to play with Idris sometimes, and they weren't always nice games, but when he was tired of her, she was free to do as she pleased.

She dreamed, in a way, of building a ship and flying it away, exploring other places, but she didn't really know what that meant – all she knew was House and Auntie and Uncle. After Nephew came along, she got some idea that there was a lot more out there than anyone was telling her, but before that… A childhood climbing over a junkyard was one filled with delight, but once Idris learned to read, she started to put names to the feelings she had. And one of them was 'lonely'.

Auntie and Uncle looked after her, because House told them to, and she'd thought this was because House cared about her, but as she started paying attention to what happened to any visitors that came to House, she started to worry. She'd thought that maybe House went fishing for ships because he was lonely too, but if that was true, then wouldn't he keep more of the people who came to stay? Other than her (and later, Nephew), none stayed at all.

Well, that wasn't true. They didn't leave, but they didn't get to stay in one piece, either. She'd seen House take people to pieces and use them for parts, the same way he did the special ships he told her about, the ones he ate. But with people, he used them to make Auntie and Uncle better, when they started to fall apart again and Idris had always thought that was because he loved them, but she started to realise that maybe that wasn't quite right when one of the harvested people escaped halfway through the process.

His ship had crashed on House after falling through the Rift and he'd crawled from the wreckage, hurt but still intact. Auntie and Uncle had picked him up, looked him over and taken him away, to the place House wanted all visitors to go. Idris didn't remember her own visit there, or why House had decided to keep her but no-one else.

She'd entertained herself, as she always did, playing with a shiny thing she'd taken from a pile of broken shiny things she didn't understand but looked pretty. Idris liked pretty shiny things. There weren't many things like that on House.

Then there'd been a terrible scream and the man had come running out – well, he'd tried to. It was hard to run when one of your feet that had been there just a minute ago suddenly wasn't. The man was doing well, though, considering. There was blood all over his clothes.

Auntie leaned out of a window in the ramshackle constructions.

"You might a told me you had the veruccas afore I took your foot, lovey!" she called.

"Just a'cos me own foot's missing all her toes don't mean I wants another defective one! And don't be going too far, now. Uncle needs a new pair a knees."

Idris climbed down from her seat atop a pile of discarded engine parts.

The man skidded to a halt in front of her, a small girl in a dirty dress, hair standing up in every direction.

"Hello," Idris said.

The man stared at her, speechless.

"You can stay in my room, if you like," she offered, pointing to the canopy stretched between two large metal sheets, under which she slept and hid all her preciouses, like the shiny thing she'd found that day. One of the sheets had her name on it, painted in curly letters like the way some of the ships that crashed had their names on them.

"But-" the man turned and looked back at where he'd escaped from, the panic written across his face metamorphosing into utter confusion.

"Oh, don't worry about them. House is busy fixing Auntie. He won't want you again for a while."

"But… my foot!"

He looked down at where the missing appendage wasn't, the stump clean and pink as if there had never been a foot there at all.

"Auntie's foot's been falling apart for ages now. She needed a new one. So House took yours. After all, you won't be needing it long."

The man looked at her in horror, this little girl talking so matter-of-factly about his dissection.

Idris nodded at the blood on his clothes, a dark spreading stain across his chest.

"House saw how hurt you got in the crash, so he decided to use you instead of fixing you. Same as your ship."

The man touched his fingers to his wound, looking at the blood as if he'd never seen it before, hadn't known that was what he kept inside himself.

Idris reached out and patted his arm.

"Don't worry, it won't hurt. Not much anyway. House is quite nice really, when you get used to him."

The man had stared at her in shock and terror for a moment, and then limped away, looking for some way out, a rescue, a way to wake up from this insane little asteroid he'd fallen onto. Idris heard him recording distress messages, like everyone did, watched him crawl around for a while, and then when he slumped down onto a heap of broken parts, holding onto his wound and going pale, she went over and sat by him. He was breathing funny and he looked tired and scared. Idris felt sorry for him, so she reached out and took hold of his hand.

"Who are you, little girl?"

"I'm Idris."

"What are you doing here, Idris?"

"I live here."

"Where did you come from? Where are your parents?"

Idris thought about it. There were flashes of memory, occasionally, so presumably there must have been parents, once. But the flashes weren't strong enough, and House wouldn't tell her anything.

"I don't know. There's Uncle and there's Auntie and there's House. And then there's me. I don't know anyone else."

Carefully, painfully, he reached out and touched a strand of her hair, as if testing she was really real.

"You shouldn't be here, Idris. This isn't a good place to be."

"I don't have anywhere else to go."

"You were brought here, from somewhere. You must've been. And… House kept you here, kept you in one piece for a reason. Do you know what that is?"

Idris didn't. She'd never thought of it like that before. House kept her here because that was how things were. House liked her. Didn't he?

"This thing you call House. It uses people, Idris. If you stay here, it'll use you too."

The man's breathing got a lot more difficult and he was putting a lot of effort into keeping on doing it.

Idris sat with him and held his hand until he stopped.

Auntie came over, walking kind of funny on her feet that didn't match underneath the shoes and started trying to pick him up.

"Oof, he's a heavy one. Still, lots of lovely stuff inside to make me and Uncle shiny and new. You need anything replacing, lovey?"

Idris shook her head.

"Suit yourself. Give us a hand with him, will you?"

And Auntie started laughing, a wheezy coughing sort of laugh because her lungs were getting old and full up again.

"Huh, give us a hand!" she wheezed. "He'll be giving us a lot more than that, won't he dear?"

Idris helped Auntie carry him back inside, then she went back to sitting on the junk pile.

Was the man right? Did House have a plan for her? Or was he just keeping her around 'til she was bigger, when he'd use her to repair Auntie and Uncle, if he couldn't find anyone else? And then there were the special ships, the ones she'd never seen herself but House talked about a lot, when he was in the mood to talk to her. He said they were getting harder to find, but that some day, when he did find one, he'd need her help. What did he mean by that?

And then, of course, one day, she found out.

It took many years; Idris was quite grown up by then. The number of ships coming by grew less and less – apart from Nephew's ship, there hadn't been any for years and years.

Then House spoke to her. He sounded pleased; he'd found one of his special ships! And now he needed Idris' help. Auntie and Uncle came and fetched her, and Nephew set up the… thingummy. It hurt, more than anything she'd ever felt before, but Idris was a good girl. She did what she was told, and it's not like she had any choice, did she? She knew what would happen if she didn't do what House told her.

The thingummy tugged at her, hard, like it was trying to pull her toes out through her brain and Idris found she didn't want to leave her body. What would happen if she did? Where would she go? She'd never get to see anywhere else if she didn't have a body to sit in, would she? And so part of her held on, some tiny spark that lingered inside the frame, hiding in the crook of an elbow, perhaps, or clinging between two ribs. And this tiny piece of what had been Idris, poor, trapped, lonely little Idris, felt the new mind and soul pouring into what had been her body, a torrent of the most astonishing power and thought and knowledge and it was all eyes, like she could see everything there was, had been, would be, all at once.

And Idris wasn't lonely anymore.

Disclaimer: No, not mine. Although if I did own anything Doctor Who or Neil Gaiman related, I think I'd just explode. In a nice way, of course.