Vale tapped the paved floor thoughtfully with his cane – which, Irene knew, was an electrified swordstick. It was the sort of equipment that Vale, as the greatest detective in London, found useful. When dealing with criminals, werewolves, vampires, cultists and spies, a prudent man took what precautions he could. ‘I know I was less than forthcoming earlier, Winters. Your new student places me in a difficult position. Catherine is your student and therefore loyal to your Library, one hopes. But she is also Fae, and the niece of Lord Silver. He might be the ambassador from Liechtenstein to the British Empire, but he’s also its spymaster in London and highly untrustworthy besides. The risk of Catherine passing information to him, deliberately or otherwise, is far too high. I simply can’t take chances on this job.’

‘I see your point,’ Irene admitted. ‘But you must have noticed how much she dislikes her uncle.’

‘Precisely the attitude I would cultivate if I were her and wanted to convince you I had no ulterior motives,’ Vale replied. He spun the wheel like the tumblers of a safe.

Irene couldn’t argue with that. ‘Very well,’ she said. ‘So, since we’re now completely alone, and unlikely to be overheard . . . What can you tell me? I should have known you had a motive for coming along, rather than just avoiding our mysterious antagonists.’ She softened her words with a smile. Heaven knew she owed him a few favours.

‘I’d appreciate your patience for just a little longer, as I would like you to approach the situation with an unbiased mind,’ Vale answered. He pulled the nearby lever down with a clang, and the airlock irised open, metal and glass petals retracting into the wall. ‘When I show you the document—’

They both fell silent. The air beyond smelled of disinfectant – but below that was the tang of fresh blood.

Immediately on the alert, Irene flattened herself against the tunnel wall, peering through the opening. Vale did the same, their conversation forgotten. The corridor beyond opened into a large room filled with mysterious machinery and radar equipment.

There was still no sound except for the slow turning of the fans.

Vale frowned. He stepped through the airlock, cane ready in his hand. Irene followed a couple of steps behind. She didn’t have a weapon on her, apart from a small knife for emergencies. But she did have the Language, a Librarian’s most powerful instrument. With it, she could command reality with a single word, and that was dangerous enough.

The chamber appeared to be some sort of control room. Heavy steel and brass switches and toggles were embedded in panels that stretched from floor to ceiling. She could also see lengths of cabling which vanished into ducts in the walls behind. On the primitive radar viewing screens, green circles fluoresced against dark backgrounds. But no targets had been identified – not that she knew what they were tracking. Two rickety metal chairs were positioned in front of the most important-looking controls, but both stood empty.

‘Stand where you are, Winters,’ Vale said. ‘Don’t disturb anything.’ He began to search the room methodically, examining the equipment. He paid particular attention to the other two passageways out of the room – also sealed with airlocks, though without any security locks of the sort that had blocked their entrance.

‘Were you expecting to meet your contact here?’ Irene asked.

‘Yes. This Guernsey monitoring station has a duty staff of six men. There should be two on duty here.’ Vale went down on one knee to check something. ‘And an additional five men somewhere within this complex. I happen to know a submarine is currently moored alongside, and the crew should have disembarked here.’

‘And the only route in by land was the one we came through?’

‘Indeed. And Dickson up on the surface, in the St Peter Port office, signalled them when we were about to come down. He received authorization for us to descend. That was only twenty minutes ago.’

A chill ran up Irene’s spine. Someone had known she and Vale would be here – trapped underground. And they’d been met by the smell of blood and the absence of allies. She refused to believe this was a coincidence, given their past few weeks. ‘This doesn’t look good for us or the staff on this station. But who is the target here?’ she wondered aloud.

‘It is imperative that I find my contact – and the document I’m here to collect. But let us exercise extreme caution.’ Vale rose to his feet. ‘The airlock on the right goes to the submarine dock, and the other one leads to the living quarters. I can perceive nothing from the clues here, except that at least one man fell to the ground and suffered a minor injury. There are also some curious scratches, which might or might not be innocent . . . This floor is not conducive to the preservation of evidence.’

‘Let’s block off the living quarters then, just in case. The last thing we want is an inconvenient ambush from that direction. Or for an aggressor to make an escape.’ Irene crossed to the airlock and placed her hand on the opening mechanism. ‘Lever which I am touching, bend sideways and out of true.’

The heavy brass lever warped until she was sure no one – no one human, anyway – would have the strength to straighten it, and another use of the Language would be needed to reopen it. She then listened at the airlock for a moment, but could hear nothing from the other side – no shouts from trapped enemies, no cries for help . . . no unspeakable slithering. She’d seen a lot in her line of work.

‘Good work, Winters.’ Vale paused at the other airlock. ‘I’ll open this one. Be ready for anything.’

He pulled the lever, the airlock opened – and three men came bursting through. After anticipating everything and nothing, Irene was almost relieved at this frontal assault. They were moving jerkily, but with unexpected speed and ferocity. Irene stuck her foot out, tripping the beefiest one of their number. He sprawled on the floor and writhed unnaturally, like a broken toy. But the other two turned to face them.

Their aggressors both wore naval uniform, as did the man on the floor. This close, Irene could see the ones facing them had smears of blood on their collars. Even more worryingly, silvery threads glittered in their irises and their faces displayed an inhuman slackness. Their mouths hung open and their heads were cocked oddly, like marionettes. One held a crowbar, and though the other was unarmed, his huge hands were clenched into fists, ready to attack.

In the distance, Irene could hear the sound of running feet. Reinforcements? Or more ‘marionettes’? She had to assume the worst. She glimpsed Vale raising his cane, but her attention was on the man lunging at her. With surprising speed, his hands went for her throat. She dodged and let him collide with the wall – but it hardly slowed him. He rose and barrelled towards her again, still moving like a puppet with hands outstretched. As she backed away, she saw a glint of metal at his throat. Something that bulged under the concealing fabric of his collar . . . and moved.

Time to finish this. ‘Uniform trousers, fall and hobble your wearers!’ she ordered.

The two men crashed to their knees, joining their companion on the floor. Irene noted that none of the three were reacting with the modesty one might expect at such an exposure. And Victorians did have a reputation for prudishness. They merely thrashed in an effort to regain their feet. Even the one who went in for purple silk underwear.