The tapping having drawn no visible reaction, Kai tried the handle. It didn’t move, so he bent over and began picking the lock. Clearly his time as a juvenile criminal hadn’t been a total fiction.

Irene spread out her skirts, and turned to watch the room, a smile pinned to her face. No, nothing going on here, absolutely normal, my friend here likes to stare into locks and wiggle bits of metal round in them, he does it every day and twice on Sundays . . .

A moment later Kai was tapping her on the shoulder, with a cool look of superiority.

Irene gave him a nod and tried the door. It didn’t explode.

This is good. I’m already ahead of the game.

She turned the handle and walked into the room. A quick glance around showed that it looked just as they had left it the last time. No sign of anyone. Nobody hiding under tables. Nobody hiding behind the door. No Alberich.

She breathed out a sigh of relief which she hadn’t realized that she’d been holding, and stepped aside so that Kai could come in. Vale followed a few seconds later, closing the door behind him.

Irene cast around, looking for anything that resembled an in-tray. Score! There was a blatantly obvious one on Aubrey’s desk. She remembered it having been tidy when they first arrived, but it was now crowded with papers and oddments. She quickly sorted through it, and the packet with the Natural History Museum’s address on the back (return to sender) was the seventh item. It was an unobtrusive package in plain brown paper.

‘Paper knife,’ she said, extending one hand.

Vale slapped a knife handle into her palm. It was elegant, made in ivory or whalebone, and had no doubt contributed to the extinction of at least one endangered species. It was also nice and sharp.

Irene sliced through the twine and unfolded the wrappings. Inside was a book and an envelope. The book’s title was Kinder und Hausmärchen. Children’s and Household Tales, she translated automatically, and breathed a sigh of relief. She flipped the book open to check the publication date: 1812. Better and better. Now what was the definite proof that Bradamant had mentioned?

She turned to the index. There were eighty-eight stories listed. The eighty-seventh was titled, in German, The Story of the Stone from the Tower of Babel.

She breathed a sigh of relief. ‘It’s the one,’ she said.

‘Yes!’ Kai said exultantly, and slammed his palm down on the desk. ‘We’ve got it!’

‘What does the letter say?’ Vale asked.

Irene put the book down again for the moment and opened the envelope. Thoughts of letter bombs came a few seconds too late. With a sigh, she shook the letter gently onto the desk. No bombs. Good.

Kai leaned across to read over her shoulder, then paused, tilting his head.

A fraction of a second later, Irene heard it as well. Screams. Screams, and a horrid sort of rustling with a nightmarish familiarity to it.

She thrust the letter into her jacket. There would be time to read it later.

The door slammed open with a heavy boom, and a woman ran in, looking round desperately. She had been amongst the browsers outside, but now looked panicked and in a state of disarray. ‘Where’s the way out?’ she gasped.

Behind her, through the open door, Irene could see more people running in all directions, but ultimately all in the direction of away. There was a spreading tide of something silver oozing across the floor in a horrible stop-motion way. It would reach a row of cases, and then it was suddenly crawling round the foundations of the next row. The noise it was making, a fierce hungry rustling and skritching, echoed in the large room, underpinning the shouting. Further back, the silver flood was oozing over ominously shaped lumps on the floor, covering them so densely that she couldn’t see the colour of clothing, hair or skin.

‘Silverfish!’ the woman screamed at them. ‘Get out of here now!’

The oncoming menace had nearly reached the chamber door.

Irene was an intelligent, self-possessed, practical woman. (Or at least, that was how she would describe herself on a performance review to any senior Librarian.) She yelped in panic and scrambled on top of the desk, pulling her skirts up and crouching there in horror. She desperately tried to remember if the Language had vocabulary for silverfish or instantly lethal insecticide and, if so, what it was.

Kai swept across the room in a motion almost as smooth as the approaching silverfish. He picked up the screaming woman, and tossed her up onto the table beside Irene before joining them. Vale leapt onto a chair.

‘You said you were here to do something about the silverfish!’ the woman screamed at Kai. ‘Why didn’t you get rid of them?’

Irene remembered her now. She’d been here when they were looking for Aubrey and found his skin instead. They’d fobbed her off with a story about insect infestation. Marvellous. She hated dramatic irony. ‘Can they eat wood?’ she asked.

‘You’re the exterminators, you tell me,’ the woman snapped.

‘Silverfish eat anything starch-based,’ Vale informed them from his chair. ‘Glue, book bindings, papers, carpet, clothing, tapestries . . . I imagine theoretically they could eat wood.’

‘If they don’t crawl up here first,’ Kai said, leaning over the edge of the table to look down at the floor. The silverfish weren’t actually trying to crawl vertically up the table legs yet, but Irene wasn’t going to wait for empirical evidence. More and more of them were now flooding into the room, crawling over each other on the floor in a thick seething mass of unhealthy silver.