Donna emerged from the TARDIS into a stupidly large room full of spaceships. The scale of it almost took her breath away. It had to be several miles wide. Fortunately they'd landed near a wall with a door set into it. Signs informed her that she was to be quiet, she wasn't to smoke, and she was to pay the parking meter or risk having her ship clamped. It was slightly chilly and she rubbed her arms to heat them a bit.

The Doctor popped his head round the door of the TARDIS. "How much is a ticket for half an hour?" he asked.

Donna read from a sign. "Fourteen splovs. Whatever a splov is."

The Doctor shook his head. "No chance." He exited the TARDIS and pulled the door closed, then stuck a sign on it saying 'DOCTOR ON CALL.'

"Bit cheeky," said Donna with a small smile.

"I am a doctor," he protested.

"Of what?"

"Never you mind." He pulled on his coat and looked around the parking bay. "They've expanded a bit since last time I was here. Used to be you couldn't get a space unless you waited for three hours."

"Or nipped into the future and skipped the queue," said Donna.

He shrugged. "Time Lord privilege. Anyway," he continued, "welcome to the Archive."

"Didn't we already do this?" asked Donna. "Library planet, every book ever written?"

"That was just books, this is everything. Every book, every film, every piece of music. Besides, this isn't a planet, it's a complex."

"But basically the same?" she persisted.

The Doctor was offended. "Look," he said, "if I can do Atlantis three times, then you can do a big library twice."

"Atlantis three times?" she asked.

"Yeah." He shrugged. "Long story. Well, three long stories." He reached the door in the wall and held it open for her.

"Do you do a lot of repeats?" she asked, ducking through the doorway.

"No, I do not! Every adventure is unique! I admit that occasionally parts of the narrative may be similar to earlier parts, but that's just coincidence. It's not like I plagiarise myself."

"So I don't have to count the shadows or anything like that?"

"Nah," he said, "this one is guaranteed safe."

()

They found a service desk staffed by a shiny silver robot with four arms and one big eye in the middle of what was probably its face.

"Hello," said the Doctor, leaning over the counter, "is this returns?"

"How can I help you?" asked the robot, tinnily. A little badge on its chest said 'I Am Delta-379, I Am Happy To Help.'

"I'm returning a book," said the Doctor, searching his pockets. "I just want to know if there's a fine." He pulled a brightly-coloured paperback from his coat and placed it on the desk. It was slightly dog-eared.

"Your card, please," said Delta-379, holding out a shiny hand expectantly.

The Doctor produced a small black rectangle and handed it over. Donna stole a glance at the book, which turned out to be the sort of romantic novel that someone might buy in a bus station. She stared at the Doctor incredulously. He didn't seem to notice.

"This book was borrowed 215 years ago," said the robot. "There is a substantial fine." Its tone made it obvious that it considered late returns to be on a par with murder.

"Oh," said the Doctor.

"He doesn't have any money," said Donna helpfully.

"Then your husband will be unable to borrow anything else until the fine is paid in full!" shrieked the robot.

"He's not my husband!"

"Apologies. Your partner/boyfriend/concubine please delete as applicable."

"He," said Donna, "is none of those things." She was getting right sick of people just assuming they were a couple.

"Don't pick a fight," said the Doctor, watching as his borrowing privileges were revoked.

"I'm just defending myself against scandalous accusations," she said as Delta-379 handed back the Doctor's card.

"I don't see what's so scandalous about it," he protested. A little red light flashed on his library card. "Ooh, I've got a message!"

"Probably just spam," said Donna.

He pressed a tiny button next to the light.

"Help us. Please, help us," said the card.

The Doctor looked at Donna, then back at the robot. "Who left this message?"

"A visitor."

"Which one?"

The robot's single eye blinked. "If it's not signed then it's anonymous."

"Fat lot of use you are," said the Doctor.

Donna touched his arm. "Keep calm. You know what you're like when you get upset. You need to be able to think properly."

They walked away from the service desk towards the depths of the Archive itself.

()

"I was a Library Monitor in high school," said Donna to break the awkward silence.

The Doctor turned his head to look at her. "Really?"

"Don't sound so surprised. Anyway, it was only for two weeks."

"Did you steal a book?" he asked.

"I got caught snogging a boy in the history section," she said with a hint of pride.

"They sacked you for that? That's a bit harsh."

"He had his hand up my jumper."

"Oh."

"Did you ever get into trouble in school?" she asked.

The Doctor shook his head. "Not for that." He looked down a long corridor of shelving and books.

Donna lapsed into silence again.

"Are you thinking of the Library?" he asked quietly.

"A bit," she admitted. "I'm trying not to."

"I'm sorry," he said. "I didn't think. I shouldn't have brought you here."

"We can't avoid everywhere that reminds me of stuff. We'd have to just sit in the TARDIS all day. Anyway," she said, "I don't want to forget all of it. Some of it was nice."

"Okay," said the Doctor, taking her hand.

"Lost Property," she said suddenly.

"What?" asked the Doctor, frowning as she shook off his hand.

"It's a big place, they've got to somewhere to report stuff that goes missing. Like umbrellas and hats and people who leave messages on library cards."

The Doctor stared at her. "Oh! Oh, Donna, you are brilliant!"

"Yeah, I am a bit," she said modestly.

"There's a Missing Persons desk, we can see if we can get into the records, find out where people were last seen. That's a much bigger needle in a much smaller haystack."

()

"Excuse me," said Donna.

A shiny robot looked up from the computer screen. This one's badge said that it was Beta-47 and that it too was Happy To Help. "Yes?"

"Can you help us? We've lost our little boy somewhere in the Archive. He just wandered off. We're ever so worried about him. Could you do an announcement or something?"

Beta-47 nodded and went to a microphone set into the desk. "Name?"

"Umm..." The Doctor looked around for inspiration and his eyes stopped on a book perched on the edge of the desk. "Arthur Dent."

Beta-47 spoke into the tannoy system. "Would the child unit Arthur Dent please report to the Missing Persons desk, your parent or guardian units are looking for you."

"Thank you so much," said Donna with maternal gratitude. Then, at a signal from the Doctor, she burst into tears.

"There, there," said Beta-47 awkwardly, patting her shoulder. "Your offspring will doubtless return before feeding time."

With the robot distracted the Doctor moved round the desk and started investigating the computer with the sonic screwdriver.

Donna wept loudly. "I love him so much," she wailed. "What if he's been eaten?"

"Eating in the Archive is strictly forbidden," said Beta-47. It produced a tissue and handed it to Donna. "There, there," it repeated.

"I told him not to wander off," she said, hugging the robot against her chest. "We lost his sister in a supermarket once and didn't see her again until she was 15."

The Doctor appeared beside them. "I'm sure he'll turn up, darling," he said to Donna.

"It's your fault!" she cried, overdoing it a bit.

"I think," he said to Beta-47, "she needs to clean herself up a bit. Is there a bathroom nearby?"

The robot pointed at down a corridor. "Please return as soon as possible."

"We will," said the Doctor, leading Donna away. "Promise."

()

"They all went missing in the 1920s," said the Doctor as they reached the appropriate section.

"That's a long time ago," said Donna. "Won't they be dead by now?"

"In the 1920s archive," the Doctor clarified.

"Oh." She looked around. "There's a lot of stuff here."

"Well it's not just Earth. That was an important time for a few civilisations in terms of art. You should have seen what the Draconians were up to."

"So is this the entire 1920s? All of it? Everything that happened?" She looked around. It didn't seem all that impressive.

"As far as that's possible, yes."

"What about Agatha Christie?"

"I expect she's in here somewhere," said the Doctor patiently.

"Do they know about the giant wasp?"

"Probably not."

"Ha," said Donna triumphantly, "finally I know more than history does!" She walked with the Doctor past a bank of computers. "I used to think libraries were safe. Boring, but safe."

"Most of them are. Safe that is. Obviously none of them are boring."

"Hmm," said Donna. She wandered down a side-corridor as the Doctor started doing whatever it was that happened when he waved the sonic screwdriver about.

"No unexpected energy readings," said the Doctor mostly to himself. "Which might mean they were physically kidnapped by someone in the Archive. I wonder why." He looked up and saw that Donna was gone.

"Donna?" he called. "Donna, stop wandering off."

There was no answer so he glanced around the nearest corner and saw a pile of magazines on the floor.

()

Someone had taken Donna. There were no signs of a struggle and she obviously hadn't had time to call for help. Someone very quick, then, or someone who seemed innocent. He looked around but he couldn't see where she could possibly have gone. There weren't any doors nearby, and a glance up confirmed that the ceiling was about a mile away.

She had to be fairly near, but he had no idea where to start looking. He was definitely micro-chipping companions from now on.

He looked up and down the short corridor, picking up the fallen magazines and placing them absently back on a shelf. He called her name a few times, not really expecting to get an answer.

Down? He dropped to his knees and pressed an ear to the floor. He could hear the heating systems at work, and the occasional squeak of vermin. Nothing there, then.

He stood up, closed his eyes and concentrated. She'd been part Time Lord for a while, once. Maybe he could sense some residual trace of that special relationship with time. He breathed in and the 1920s wobbled slightly, imperceptible to all but his own kind. He thought of the 21st century, of the way it sparkled on her skin. His feet moved and he opened his eyes to find himself facing a door that he'd have sworn hadn't been there a minute ago.

Acquisitions.

()

Donna lay stretched out on a raised surface with electrodes stuck to her face. There were at least fifty people lying in rows alongside her. The Doctor rushed over and then stood staring impotently, unsure if it would be safe to disconnect her.

He heard footsteps behind him. "Give her back," he said without turning. "Give all of them back."

"I'm afraid that isn't possible," said an old voice.

The Doctor spun round. "I think you'll find that it is," he said angrily. He glanced back at Donna. "What do you want with her?"

"She has certain specialist knowledge of areas where there are... gaps... in the Archive."

The Doctor remembered her mentioning Agatha Christie's wasp. "So?"

"There can be no gaps," said the man with the old voice. He was tall, blue-skinned, and had slightly terrifying teeth. "The Archive must be complete."

"You can't just kidnap people because they know things that you don't. Can't you just ask them to write it down for you?"

"This is the easiest way, for everyone." The man smiled sadly. "The memory cheats." He nodded to the Doctor. "I represent the Acquisitions Committee. It is my sworn duty to help make the Archive as reliable as possible." He stepped forwards. "Perhaps you could help."

The Doctor took a step back. "Okay," he said.

"Really?" The blue man raised his eyebrows. "We don't get many volunteers."

"Let these people go and you can have all you ever wanted to know about Gallifrey."

This was apparently the right bait. "Gallifrey? That information became unreachable at the end of the great Time War."

"Not for survivors."

"There weren't any."

The Doctor sucked air in through his teeth. "My, my, now that's what I call a gap in the Archive."

The man hesitated. "If I could consult with the Committee..."

"Nope," said the Doctor, "this is a one-time offer, take it or leave it." He moved closer. "But I expect they'd be quite pleased with you if you managed to get them a living encyclopedia of the lost secrets of the Time Lords."

"Then come this way."

()

The Doctor pulled the electrodes from Donna's skin carefully. He checked her pulse and concluded that she was just sleeping.

"Donna? Donna, time to wake up."

He waited for an answer, but she didn't move.

"Do I have to do the Sleeping Beauty thing?" he asked, trying to hide his panic.

"No, you bloody well don't," said Donna groggily as she opened her eyes.

He grinned and hugged her as she sat up. "You had me worried."

"Did I?" Donna looked round. "Where am I?"

"I'll get someone to explain. I have to go and keep my end of the bargain."

"Bargain? What bargain?"

"I sort of... swapped myself for you." He held up his hands to stop her protesting or hitting him. "Don't worry, I've got a great plan."

"What is it, then?"

"A secret plan," he told her evasively. "I'll be fine."

()

Donna watched the Doctor settle on one of the raised platforms, sticking electrodes to his forehead. "I can't believe you're doing this," she said. He'd said he had a plan but what if that was just a clever lie to shut her up? She took his hand. "If you leave me stuck in this place forever, I'll kill you myself."

"Just trust me," said the Doctor, giving her a quick wink.

Donna stepped back as the process started. The tall blue man with the pointy teeth stood beside her, a greedy look in his eyes. He went to a monitor and watched whatever was going on inside the machine.

"Contact has been made," he announced, not bothering to hide his excitement. "Uploading."

Donna looked at the Doctor, but he didn't seem to be doing anything other than breathing. Come on, Spaceman she thought to herself, Do something impressive.

"Wait!" said Blue.

Donna turned. "What?"

"What's he doing to the 1960s?" cried the man. He rushed about pressing things and shutting off alarms.

Donna looked at the monitor and tried to make sense of the words on the screen. After a few moments she understood – the Doctor was deleting information from the Archive.

"I suppose that's a bit impressive," she said to herself.

"I have to disconnect him," said the man, "he's damaging the system!"

The Doctor sat up suddenly, tearing the wires from himself. "I think I've made my point," he announced.

()

"Well," said Donna, "I suppose the 60s were a bit dull anyway."

The Doctor looked scandalised. "No! They were great! You just have to approach them on their own terms."

They were back at the TARDIS now. Donna stood as the Doctor rummaged in his pockets for the key. She took the sign off the door and handed it to him. "At least we didn't have to pay for the parking."

"Yeah. I really wish I'd been able to get them to waive that late returns fee though."

"You did ruin their library," she pointed out.

"It's only gaps! Everyone's got gaps in the story somewhere! I can barely remember 1967 myself. And then there's that weird stretch in the 1990s where not much really happened..." He shrugged. "They'll get over it."

"In any case," said Donna, "I've learned an important lesson today."

The Doctor unlocked the door of the TARDIS. "And what's that?"

"If the book's that late... you might as well just keep it."