While Kingsley wrestled with astonishment he followed Evadne straight to the largest steel cabinet in her workshop. It was vast and the no-nonsense grey colour favoured by the military when it wanted to be serious.

‘Now,’ she said. ‘Before we confront these Immortals, we must prepare.’ She looked gravely at Kingsley. ‘I always prepare, don’t you?’

‘Of course. Preparation is the key to success – but wait a moment.’

Evadne flung open the cabinet doors with a crash and stood in front of them with her hands on her hips. ‘Yes?’

‘You want to kill these Immortals.’

‘That’s right.’

‘The undying, evil, powerful, magical, vastly rich sorcerers?’

Evadne bit her lip. ‘Kingsley, just come out and say it if you don’t want to go. You can stay here. I think I have the remains of a seed cake in the cupboard.’

‘It’s not that. I just think you’re being a little precipitous.’

‘Precipitous? This isn’t precipitous. Yesterday was precipitous.’

‘The Spawn in the sewers?’

‘My temper had the better of me.’ She closed her eyes briefly. ‘Kingsley, I’m doing my best to approach this calmly, because the alternative is launching myself at those horrors in a mad rage, despite the danger.’

‘Your crusade is that important.’

‘Important? At times, it’s overwhelming.’ She bit her lip before continuing. ‘I’ve known about these Immortals for a long time, Kingsley. Going up against them isn’t a lark. They’re murderous, deadly, and very, very powerful.’

Kingsley knew that Evadne was spelling out the peril for him. ‘And yet you’re determined to confront them.’

‘I have no choice.’

Evadne turned back to the cabinet, leaving Kingsley in a welter of confusion. He wanted to find his foster father, but with events conspiring as they had, he knew he needed help. In addition, there was Kipling and his hints about the Immortals and their plans – unspecified, but assumed to be of dreadful import – concerning the Olympic Games. And here in front of him was an undoubtedly troubled Evadne, setting off to confront these selfsame wizards.

When trapped in the dark, manacled in a chest with water pouring in, Kingsley knew that the best thing to do was to decide on a single course of action and to stick to it. Trying to do a number of things at once was the way to a disastrous end. Here, his course was clear. He had to help Evadne, and by helping her he’d gain an important ally in the search for his foster father.

‘What’s in the cabinet?’ he asked.

‘Necessary equipment.’

She stood aside, and Kingsley had his first real look at what the cabinet contained.

The objects he was looking at must be weapons, for nothing else in the universe had that combination of elegance of design and utter deadliness in a neat, manageable package. Death-dealing in one hand. Or two, as he took in some of the larger devices.

Someone had taken the basic components of metal, wood and a smooth black substance like jet and constructed a few dozen weapons that glittered and smelled of oil and destruction.

‘You’ve had firearms training?’ Evadne selected a long-armed number that had more glass than Kingsley was accustomed to in a rifle. It also sported various knobs, chambers and levers that should have made it look ridiculous but instead made it look as if it could annihilate regiments once it warmed up.

‘Some.’ Kingsley fancied himself as a marksman and had once been a member of the school’s Rifle Brigade, but he’d always preferred target shooting rather than the prospect of hunting.

‘Good.’ Evadne slid open what Kingsley assumed was the breech and inspected it. ‘At least you’ll know which end to point where. After that, you shouldn’t have to worry.’

Kingsley reached for one weapon that was mostly brass, including a skeleton-like stock.

‘Not Neptune’s Trident,’ Evadne said. ‘It’s for underwater use, and I don’t anticipate we’ll need it where we’re going.’

‘Neptune’s Trident?’ Kingsley blinked. ‘Do you have anything rather less . . . outlandish?’

Evadne shrugged. ‘I didn’t think I was being outlandish when I made them. I was just having some wicked fun.’

Kingsley had become well acquainted with astonishment in the last few days, so he recognised it when it jumped up and hit him between the eyes. ‘You made these?’ He surveyed the wreakers of mayhem in front of him. ‘I thought you must have bought them from one of your Demimonde people. I was imagining a secret tribe of weaponsmiths, Brotherhood of Vulcan or the Hammerhead Boys or suchlike.’

‘Oh, I had some help with some of the components, and there are some remarkably fine engineers in the Demimonde, but they’re all my own design. They’re all bespoke, you see.’

‘Mmm.’

‘I do hope you’re not still judging by appearances.’

‘Me? I’m more than happy to believe that what lies underneath the surface is important.’

‘Good. I just happen to be excellent at engineering design as well as juggling.’

‘Naturally. Of course. Makes perfect sense.’ Kingsley ran his hand over the compact shape of what could be a handgun, if handguns were the shape of a seashell and as lethal as a cobra. ‘These are works of art. What about this one?’

‘Midnight’s Kiss? That’s fine. Just be careful of that button.’

‘Which button?’

‘That button. The one you just triggered and made the spike punch through the top of the cabinet.’

Kingsley saw no point in denying it, since the evidence was clear. ‘That cabinet needed an airhole, anyway.’

Gingerly, he touched the button – just next to the safety – and the six-inch blade slid back into a neatly concealed slot. He hefted the pistol – which was really more of an elongated disc than a shell shape – and was impressed at how light it was. He hoped it would be enough to combat immortal sorcerers and their underlings. ‘Do you have names for all of your weapons?’

‘It’s part of the fun.’

Evadne was once more entirely blithe, as if preparing for a Sunday picnic rather than a mission of mayhem, but Kingsley was concerned at the brittleness of her guise. ‘What about ammunition?’ he asked.

‘For that one? Over there, fourth drawer, second from the left. The magazines are already loaded.’

Kingsley found the ammunition cabinet as Evadne had said. The smell of gun oil was heavy, and each of the many drawers was neatly labelled with numbers that were ominous in their anonymity.

He paused. ‘You do seem to have expended much ingenuity on devices of destruction.’

‘My weapons?’ She gazed around. ‘I suppose so. In the Demimonde, though, prominent means of self-defence are always useful.’

‘Self-defence? All this is for self-defence?’

She shrugged. ‘I became carried away.’

He didn’t know what to make of Evadne. A juggler, a wit and a genius? Any two would be overwhelming, and he had the feeling that three wasn’t the end of it.

He found the correct drawer. The magazine was the size of an omnibus ticket, but heavy. He wasn’t surprised when it slotted perfectly into the pistol. Half a dozen others were in the drawer, and he took them all.

‘Don’t forget to select a knife.’ Evadne pointed at another cabinet, to the right of the ammunition store. ‘Knives don’t run out of ammunition.’

‘You make knives, too?’

‘Those, I buy. I know my limitations.’

You might, Kingsley thought, but I certainly haven’t found them yet.

Evadne crossed the room and tapped at the bare wall. A door swung back to reveal a safe.

The safe was waist high and looked as if it had been designed to discourage burglars simply by its looks. ‘Don’t waste your time,’ the solid metal bulk seemed to say. ‘I am impervious,’ its dull grey colour announced. ‘Why bother?’ the many dials and knobs on the front insisted.

After a complicated series of twistings and turnings, the safe swung open. Evadne found what she was after and heaved it shut with a neat hip swivel that did alarming things to Kingsley. He looked away and concentrated on his knife selection. Far less dangerous.

Evadne came to his side. Her presence was, he admitted, agreeable. ‘Take the one on the end.’

‘The one on the end? They don’t have names?’

‘I only name that which I make.’

Kingsley was about to follow this intriguing delineation when a horde of small furry shapes shot through the open door and raced directly at Evadne.

He had his knife in hand before he saw that there were only six of the creatures – enough for a horde, in his mind – and that they were Evadne’s myrmidons.

He relaxed and tucked his new knife away.

‘I was wondering what was taking you so long,’ Evadne said to her minions. They swarmed about her feet, some rising on their back legs in the ecstasy of seeing her. She crouched and patted them, distributing her affection evenly.

This time, Kingsley made an effort to study them, even though something deep inside him wanted to pick them up by the scruff of their necks and give them a short, sharp shake.

Each was the size of a cat, but after that they did conform to his notion of a rat, apart from half of them having three eyes. They had the snout, the scaly tail, the brown fur that suggested they were, indeed, descendants of those who were the Black Death’s best friends.

‘They’re half-machine and half-animal,’ Evadne explained. ‘They’re my first experiment with this sort of hybrid. It’s a very difficult area.’

‘So I’d imagine.’

‘Not just technically, although it’s a nightmare to mesh the biological parts with the non-biological. I meant that it’s difficult ethically. These creatures are stronger, quicker, more intelligent than they were, but I’m still not sure whether I have the right to do what I have.’

‘I’m impressed that you’re troubled.’

‘What do you mean?’

‘I imagine inventing types lost in the enthusiasm of projects, not giving a fig for questions like this. I’m happier with someone who’s thoughtful.’

Before she turned her head away, Kingsley was sure she blushed. It was only a soft pinkening of her cheeks, but he was certain he’d seen it.

‘Kingsley, would you please fetch me some of the excursion biscuits? They love them. They’re in the Huntley & Palmers tin.’

When Kingsley came back with the tin, the myrmidons had gone. ‘Where are they?’

Evadne spread her hands. ‘They were so eager to be off on their mission, they wouldn’t even wait for a biscuit.’

‘They have a mission?’

‘Among other things, I’ve sent them looking for any signs of those inimical to the Immortals. The League of the Righteous. The Supplicants. The Aaconites. No-one has heard of them for years, but my myrmidons are persistent.’ Evadne opened the tin and took out a biscuit. ‘Almond ring. My favourite.’

Kingsley was dazed. Try as he might, he found it hard to keep up with Evadne. It wasn’t an unpleasant sensation; he found himself wanting to rise to the challenge that she was. ‘One thing that puzzles me . . .’

‘Only one? What a happy state you must live in.’

‘One thing will do for the moment: what on earth are you doing in the theatre?’

Evadne looked at him solemnly for a moment, then she re-racked her weapon of choice – a pistol that looked mostly to be made of crystal. She reached into a pocket of her riding jacket and produced a handful of brass cylinders – shells, of a sort, but where the bullet looked nothing like lead. Kingsley wondered if they were some sort of incendiary rounds, but at that moment, Evadne began to juggle.

Slowly at first, two, then three of the brass cylinders glittered, arcing from one hand to the other. They were joined by one more, then another. ‘I enjoy the theatre,’ she said.

Kingsley applauded, helplessly. He admired dexterity and when it was allied with grace, it was doubly impressive. ‘You’re excellent,’ he said, ‘but that’s not what I mean. I understand the thrill of performance, the challenge of entertaining people, but when you have this –’ he swept an arm around the cabinet-filled room – ‘why wouldn’t you devote yourself to inventing?’

She made a face and with three quick motions the shells disappeared back into her pocket. ‘A question for a question. How many female inventors do you know of?’

‘I don’t know of many inventors,’ he admitted.

‘Scientists, then. Or engineers. What about your foster father’s colleagues? How many women academics are there?

‘Ah. I see.’

‘And that’s not to mention the opprobrium from my family.’

‘Are you saying they’d rather have you on the stage than working in science?’

‘I don’t know. When it was clear that they wouldn’t favour either, I left them to their own devices.’

‘You ran away from home.’

‘That makes it sound rather more rapid than it was. I walked away from home, head held high, with a thousand plans in my head and Montague Dobbs waiting for me.’

‘Montague Dobbs. What about Clarence?’

Evadne touched the chain around her neck. ‘Clarence never knew about Montague Dobbs.’

‘I expect he wouldn’t,’ Kingsley said. Why hadn’t Evadne spoken of this Dobbs fellow before? ‘Well,’ he said with an effort at briskness. ‘I’ll need some sort of rucksack, if we’re to equip ourselves properly. And rope. Do you have any rope?’

Evadne laughed, but indicated a cabinet near the door. ‘Rope is in that one. You’ll find a selection of rucksacks in the drawers underneath.’

‘Thank you.’

‘Your face has the virtue of being wonderfully open,’ Evadne said. ‘Mostly.’

‘And where is this Dabbs fellow?’ Kingsley busied himself in choosing an appropriate coil of rope. Jute or manila? ‘Why isn’t he here to help you on this expedition?’

‘Dobbs, not Dabbs.’ Evadne stifled another laugh. ‘He’s not here because he’s not real. I made him up, years ago.’

‘I beg your pardon?’

Evadne had a hand over her mouth, but her eyes danced. ‘Montague Dobbs is the holder of a number of lucrative patents and the owner of several companies. Since minors can’t hold patents, sign contracts or generally do business, I needed someone who could.’

‘What about your father?’

‘Oh no, I couldn’t let him know about my doings. I’d disappoint him dreadfully. He wants me to be dutiful.’ She closed the gun cabinet. ‘I invented Montague Dobbs. Quite a wealthy man, is Dobbs, but he’s rather a recluse.’

‘You can’t just invent someone out of thin air. A company director must have meetings, needs to talk to bank managers.’

‘I have an actor to do that. A discreet fellow. And he’ll continue to be discreet if he wants the generous fees I pay him.’ She opened another cabinet and paused in front of a collection of swords. ‘Most of my business is conducted through the post. His Majesty’s Postal Service is rather more reliable than even the best of actors equipped with the most superb of scripts.’ She selected one of the blades. ‘I do love a sabre, don’t you?’

‘I’m astounded.’

‘I can tell.’

‘So you paid for all of this through your patents?’

‘I’ve licensed – sorry, Montague Dobbs has licensed – a number of patents useful in the optical industry.’ She belted on her sabre then tapped her spectacles. ‘I’ve also allowed them to be used in astronomical research.’

‘You’re rich.’

She rolled her eyes. ‘Rich enough. The financial speculation helped.’

‘Naturally,’ Kingsley said desperately.

‘Bonds, consols, that sort of thing. I’d rather have my money working for me than not. Daddy is enormously wealthy, but I wouldn’t touch anything of his. After some lean times, I’m now wealthy enough to do what I want.’

‘Which is to invent things and to go on the stage.’

‘I couldn’t have a retreat like this if I didn’t invent things.’

‘Of course not. It must have cost the earth.’

‘It wasn’t cheap.’ She made a few ghostly juggling motions with both hands. ‘Everything here is powered by a revolutionary source.’ Small dimples creased the corners of her mouth. ‘It’s called phlogiston.’

‘Oh, phlogiston.’

‘You’ve never heard of it, have you?’

‘Not in this context, no.’

‘In what context have you heard of it?’

‘None, really. I was just trying to give myself some time to cudgel the old brain to come up with something.’

She eyed him with cool amusement. ‘Phlogiston was thought to be the vital part that materials released when burning, which explains why something burnt couldn’t be reburned. And don’t say “but”. This was early chemistry, remember, and really has nothing to do with what we call phlogiston, which is a magical fluid that can be extracted from air.’

‘Magic.’

‘We’re in the Demimonde, remember? Some magic works. Some of the time.’ She wrinkled her brow. ‘Phlogiston is tied up with the Immortals, strange to say. Neo-Platonism anyway. They say that phlogiston is the exhalation of the Earth. It’s the outpouring of the supernatural entity of which our planet is only a physical manifestation.’

Kingsley looked at her blankly. ‘That makes no sense.’

‘It makes perfect sense, just not a sense that you’re accustomed to.’

‘So you use phlogiston to power this place?’

‘I invented a neat little phlogiston extractor, much better than the stuff I could buy out there. It’s hideously expensive, which is my point.’

‘I’m sure.’

‘Did I mention that it’s also highly explosive?’

‘No, but I have no trouble accepting it.’

‘Wait here.’

Evadne went to her safe again. She returned holding a glass vial, the size of a finger and glowing red. She was smiling. ‘Phlogiston.’ Then she pulled another vial from the pocket of her robe with a flourish. ‘More phlogiston.’ Then she leaned over and, with a capable piece of sleight of hand, pulled another vial from Kingsley’s ear. ‘And more phlogiston.’

With another smile, a different one this time, rather more professional, Kingsley decided, she began to juggle them.

She began slowly, sending all three vials in an easy loop, then she began tossing them higher, plucking them out of the air, passing them behind her back, showering and cascading them, faster and faster until the glow was a blur.

Kingsley was impressed and alarmed. He hesitated, not wanting to break her concentration, but he had to ask: ‘Didn’t you say this stuff was explosive?’

‘It’s safe in the right hands, which mine are.’

With a toss of her head, Evadne launched all three skywards. She caught the first in her pocket, the second behind her back and the third fell perfectly into her upraised palm without her looking at it.

Her eyes were bright and she was breathing fast. She held up a finger, asking for a moment, then she answered. ‘Under the right circumstances, it’s highly explosive, which means with a correct detonator and such. With the right preparation, a hundred different effects can be achieved, thanks to phlogiston’s remarkable qualities.’

‘What happens if you drop one? The glass would break and then what?’

From the look on her face, Kingsley immediately regretted the fact that words didn’t have strings tied to them so he could have tugged back the questions he’d just asked.

‘Firstly,’ she said, ‘I don’t drop things when I juggle. Secondly, these aren’t simply glass. They’re embedded with phlogiston itself for extra strength.’

‘I’ve never seen a better juggler.’

She curtseyed. ‘I thank you.’

‘Remarkable stuff, that phlogiston.’

She leaned close in her enthusiasm and Kingsley could appreciate how fine her eyelashes were, as if they were extracted from the breath of snow. ‘It’s what I used to collapse those tunnels, the ones the Spawn were using to get to us, to make sure we are safe here.’

‘Versatile stuff.’

‘Even more exciting, I’m working with anti-phlogiston.’

‘And why would you do that?’

‘Apart from pure scientific rascality? It’s exciting, that’s why! Something that is equal and opposite to phlogiston must have enormous potential. Apart being extremely antagonistic to phlogiston, which is rather too obvious to be interesting.’

‘So that’s science. What about the theatre?’

She narrowed her eyes at the sudden change of topic, but replied. ‘I love the theatre, but, to tell the truth, it serves another purpose.’

‘I’m surprised. Everything else has been so straightforward.’

‘Another bon mot. You’re rising to the occasion, Kingsley and I’m glad. I thought you might be becoming Byronic, swanning about all gloomy and handsome.’

‘I tried being Byronic once, but it gave me a headache.’ Kingsley was trapped inside a whirlwind, but he was determined to keep up. ‘You were telling me how the theatre had a double purpose for you.’

‘Most of those who exploit children end up in the Demimonde, so I needed access to it. The theatre was my entry.’ She made an odd gesture then, putting both hands side by side, palms up, then bringing them together – as if she were closing a book.

Kingsley decided that it was clearly the end of the matter.

‘This mission,’ he said. ‘Are you sure you’re doing the right thing?

‘Sure?’ Evadne’s lightness of mood fell away. ‘Hardly. I’d love to live a life of certainty, but it’s not for me. I live a life of maybes, perhapses and howevers. Nothing is certain.’

‘Which gives room for hope.’

She touched his cheek. ‘Now that, Kingsley, is just what I needed to hear.’