– ‘I didn’t ask for any of this,’ he went on smoothly. ‘I would much rather have simply taken the book and left. No mess. No fuss. So I’m asking you, in a perfectly reasonable way, to stand up straight, stop stammering, and give me a full report. Imagine I’m one of your superiors.’

He could have been one of her superiors too. It was easy to imagine. They were diverse enough – such as Coppelia with her clockwork limbs or Kostchei with his thousand-yard gaze. But all had the same air of authority that Alberich was displaying. Other than that and the rumours, she knew nothing about him. She didn’t even know what he looked like. And he terrified her.

‘Under the circumstances—’ Vale put in.

‘Remember that I can and will freeze your vocal cords too,’ Alberich said. ‘And your lungs. Unless you want to explain events yourself? In which case, Ray here becomes worthless . . .’

‘I believe Miss Winters can handle this,’ Vale said. ‘I will only interrupt if I have something important to add.’

He was probably used to coping while people held knives at his throat, Irene reflected savagely. ‘Allow me,’ she put in. ‘I believe that the main factor here was that Wyndham knew too much.’

‘Quite a claim, given how much Vale seems to know of Library business,’ Alberich said pleasantly.

Irene decided to ignore that as she wondered how long Kai would take. And would she know when he’d finished? She needed to spin this out as long as possible, weave all her guesswork into a convincing narrative, and pray that Alberich would accept it. ‘Wyndham had connections with the Fae,’ she started confidently, ‘but he also knew that Dominic Aubrey was a Librarian and, as such, opposed to the Fae. Wyndham knew the book was significant to Silver and thought that he could use it as a bargaining chip to gain something in return. Or he might have been taking some sort of complicated revenge. It was one of those Fae relationships. He decided to make sure that the book was somewhere safe while he negotiated. So he sent it under cover of another parcel to the Natural History Museum.’ Could she persuade Alberich to go there to look for it? ‘And then he was murdered.’

‘Oh yes,’ Alberich said. ‘I arranged his killing. My agents didn’t find the book while they were there, but that would be because Belphegor got there first. The Iron Brotherhood were extremely useful. Vampire-killing assassins, automata to send after you, and other things too. It seemed the easiest way for me to get hold of the book. I didn’t feel like dealing with Silver or the other local Fae. Some of my allies have issues with certain factions. But I won’t bore you with the details. I entered this alternate, took control of the Iron Brotherhood, found the locally stationed Librarian, questioned him, and assumed his skin. Simple enough. Speaking of that, do you still have it?’

Irene abruptly wanted to be sick. She’d maintained some control during werewolf attacks, zeppelin near-crashes and silverfish fatalities, but this was different. Questioned him. Assumed his skin. ‘It was you, wasn’t it? The first time?’

He understood her question, ill-formed as it was. ‘Oh yes. I was the one who met you and your student when you first came through. To be honest, you’ve been rather a surprise to me.’

‘Flattery will get you nowhere,’ Irene said primly, counting seconds in her head.

Something else was clearly ticking over behind Alberich’s eyes too. ‘If you’d found the book in the Natural History Museum, you could have gone straight back to the Library by forcing a portal elsewhere. You wouldn’t have needed to come here. And you’ve admitted Wyndham knew that Aubrey was a Librarian. Answer me, Ray. Did Wyndham send the book to Aubrey?’

‘Yes,’ Irene said. The word came grating from her mouth in response to his question and his use of her name before she could waltz around the subject any further.

A high colour showed on Alberich’s cheeks. It must be some sort of anger-reaction transmuted by the skin he was wearing. ‘Are you telling me that the book came here?’

Irene could feel the response dragging at her throat, trying to say itself. Vale’s eyes met hers for a moment, as she weighed the benefit of distracting Alberich further against the risk of his cutting Vale’s throat if he lost his temper. ‘Yes,’ she said quickly, giving in and letting the word out, before Alberich felt the need to make good on his threats.

‘And it’s the book on the desk?’

Irene opened her mouth to deny it, but couldn’t. The word dragged itself from her lips. ‘Yes.’

Alberich exploded. ‘You pitiful little idiot! Do you have any idea how much effort I’ve had to put in here over the last few days?’ He was shrieking like a harridan, and though the knife at Vale’s throat was steady, his face was wrong – his mouth open a little too wide, his eyes staring furiously, spittle spraying the side of Vale’s face. ‘I shift skins twice. I take my attention away from very important projects. And because you have been running around hiding this book, my efforts have been wasted. Do you think that’s funny, Ray? Do you?’

The room began to shift and crawl around him. The papers on the desk ran into liquid and dripped away, running down to splash against the floor. Dead silverfish dissolved into vapour that blew outwards in widening curls, as though Alberich and Vale stood at the centre of a whirlwind. The panes of glass in the display cases began to vibrate, thrumming as if someone was singing at an impossibly high pitch. And now Irene could feel it pulsing at the back of her skull, humming in her ears. ‘Stop it!’ she cried out.