"What's in there?" Rose asked, pointing to the door opposite them as they exited the music room. It caught her eye because it looked different from the rest. The wood was darker and it looked far more solid and secure.

The Doctor carefully shut the door behind them before glancing up to see what she was referring too. There was a flicker of emotion on his suddenly taut face and Rose immediately felt bad for asking. Clearly whatever it was, it wasn't something he was comfortable with.

He stared at the door for a long moment, but to Rose it appeared more like he was looking through it into whatever was beyond. And he certainly didn't like what he saw.

"It's alright," she said, touching his arm lightly, "We can go somewhere else."

"No," he said determinedly, "You should see."

He strode over there in a purposeful manner and Rose had a feeling he was facing some kind of personal demon in doing this.

She was really beginning to wish she hadn't asked now. They'd been having such a nice time and she'd just ruined it.

She watched carefully as he paused with his hand on the door handle, staring at it intensely. She stepped up beside him, placing her hand over his. A silly little gesture really.

"Whatcha waiting for?" she asked, gently.

He gave her a soft smile, "A bit of courage."

He glanced briefly down at her hand on his, "And I think I found it."

Without further hesitation he firmly turned the handle and let the door swing open. Rose peered inside, a little fearful of what she might see but confident that she was safe with him around.

The lights flickered on one by one, leading her eye line down a long gallery like room, with a high white ceiling and grand granite columns. Wooden, glass fronted display cases lined the walls and were peppered at intervals on the antique wooden floor. She frowned, stepping inside as a realisation struck her.

"I've been here before."

"Yep," the Doctor said, following her in, "It's a perfect copy of the King's Library at the British Museum. Well, technically they copied us."

She looked at him curiously.

"Long story," he muttered, brushing the matter away.

Rose had been there once before, on a school trip to look at the Elgin Marbles. Or, as she had put it, a lot of headless guys who had nothing to write home about down below. She remembered thinking that this room was pretty cool though – not that she would have dared said it out loud. Her friends never would have let her hear the end of it.

What was in here that the Doctor was so afraid of, she wondered. Glancing back at him, his face was set in an unreadable mask and she didn't feel confident enough to ask him outright. Some instinct in her gut told her it was something very unpleasant.

She took a few more hesitant steps in, glancing around apprehensively. The air in here was stale and mildly musty as though no one had been here for some time. The display cases appeared to contain a totally random collection of items, most of which she didn't recognise and so assumed they were alien. Glancing around though, one thing in the case to her left did strike her as vaguely familiar and she stepped closer, her nose touching the glass as she peered down to get a better look at it. She was just about to ask the Doctor where she'd seen it before when the memory hit her.

Van Staten had had it.

The Doctor had told him it was a musical instrument and shown him how to play it. The sound had been beautiful. In everything that had happened afterwards she had simply forgotten about it until now.

Why had he brought it here? Why had he kept it? She hadn't seen him take anything else from Van Staten's museum. Why this little thing?

As she turned back to ask him about it, her gaze fell upon something else and her heart thumped almost painfully in chest. She drew in a sharp gasped breath and found herself suddenly unable to move.

It was charred and twisted but there was no doubting what it was. A dinner plate sized piece of Dalek armour.

She turned to the Doctor the dark look on his face mirroring hers.

"Where did you get it?" she asked quietly, swallowing hard.

"Before the Time War," he said purposefully not looking at the object, "I was studying it to try to find out more about Dalek construction. We thought we could find a way to stop them."

"Why's it here?" she questioned, totally perplexed.

"Because it's all that's left," he explained softly.

And in an instant, Rose understood what this was all about.

"Everything here," she said, an overwhelmed look on her face, "All these planets are gone, aren't they?"

He nodded tightly.

Rose shook her head, barely able to take it all in. It was just too much. This room had to be three hundred feet long and every case she saw held something. It was like a memorial. A tomb.

"What happened to them?" she asked, tenderly, "The Time War?"

"Most of them, yes."

"How many?"

"I don't know for sure. Just short of two hundred, I think."

She nodded, trying to comprehend it but struggling. The only other time she had felt like this was when she had stood on that space station watching parts of her former planet drift by. It was just too big for one person to get a grip on. Every time she thought she had it straight in her head the solid idea she had fixed on seemed to vanish and mix in with the jumble once more.

Two hundred planets. That was billions and billions of people. Aliens. Whatever. All dead. Their societies, memories and cultures all gone and everything that was left locked away and collecting dust in a time machine floating through space.

It wasn't right. But it was something.

A thought crossed Rose's mind and she asked him before she realised that she probably shouldn't.

"What about your world? Is there anything in here?"

He nodded, grabbing her hand and pulling her gently towards a nondescript case to the right. He pointed inside and it took her a moment to realise that he was indicating a small, dull looking metal disc that didn't even seem to have pride of place amongst the other contents.

"What is it?"

"A coin," he said simply, "Worthless really. It wasn't even legal tender by the time the war happened. We got rid of the need for money centuries before that."

"Where'd you get it then?"

"Private collector. I helped him out with a giant paralysing bug invasion and he gave it to me. He said it was only right I have it."

He smiled slightly, "It's odd really. As far as I know it is the only thing left, apart from the TARDIS of course. And it doesn't exactly represent who we were."

"But it's better than nothing," Rose pointed out.

He nodded, grateful for her presence, "It's better than them being forgotten."

Rose looked thoughtful for a moment, before sticking her hands in her jeans pocket and pulling something out. It was a penny she'd carried with her everyday for years. She'd found it in the park the same day Jimmy had been arrested for robbery. She'd cried for hours then, realising what an idiot she'd been and scared that she'd screwed up her whole life. She'd found it as she had walked back home. Picking up a coin was meant to be lucky and she certainly felt in need of some. It hadn't always worked but she carried it anyway through force of habit.

"Do me a favour," she said, pressing the coin into his hand, "Put that in there too."

He looked at her curiously.

"I've seen the end of the world," she explained, "But it wasn't my world. Not really. I mean, look at Cassandra. If she's the closest thing to human left by then, I don't want it to be remembered that way. It wasn't who we are. Who I am."

The Doctor nodded, understanding the need to leave something behind. He opened the case and slipped the coin inside, laying it next to its Gallifreyan counterpart.

"You should probably get some sleep," he said, unable to tear his eyes away from the coin, "You look pale."

"What about my surprise?" she asked gently.

"Tomorrow," he promised.

Rose nodded, understanding. There were sometimes when he needed to be alone.