Light flared at the back of the control compartment. Damona tore away the steel cover plate too late.

The machine exploded.

Later. Damona on her back, looking up. Pain. She choked on the smoke. She rolled, stood, coughed, winced at the pain in her hip. Her hair had come undone. It hung over her face. She heard shouting.

A draught. The smoke began to move. Damona grunted. Someone had opened the steel doors at either end of the workshop. Good thinking.

The smoke cleared. She squinted, batted it away. She peered up past the gantry crane and its rails to the ventilator shaft. She swore. The screw turbine had shattered. No more air from above until it was fixed. She shuddered. Metal shards must have sprayed through the whole workshop. She’d been lucky.

She grunted again. Death wasn’t for her. Not yet.

The smoke had gone. She screwed up her nose at the smell of charred insulation. She laced both hands in the middle of her lower back. The old hip injury was flaring, too. She felt every one of her two hundred years. She growled and studied the remains of the machine she’d been working on.

It was a wreck.

She plucked a screwdriver from the bench as she passed. Then: careful stalking towards the wreck. Big steps over casing panels that had been blown aside.

She prodded at the steel and brass machine. What had she been doing just before the explosion? After months of work, what had gone wrong? The principles were right. She knew it. Implementation was at fault.

Was she becoming less dextrous? Age catching up with her?

She stood back, hands flexing, taking stock. The original lines of the extractor were still there. She’d avoided straight lines and corners. The flanks of the wagon-sized machine curved like wave-worn rock. Both sides rolled around to grip the control panel at the end. She shook her head. The control panel that was now a mess of melted glass and metal. The top third of the extractor had been sheared off by the explosion. The contours she’d been so satisfied with were no more.

She stood on tiptoe and nearly cried. Inside, the machine was ruined. She tried to remember where she’d left the plans, her notes, her grand scheme.

‘Hurt?’

Damona didn’t look around. Could she salvage that thermal bridge? ‘No, Gustave.’

‘What happened?’

‘Phlogiston uptake error.’

‘Dangerous, that.’

Damona almost laughed. Phlogiston was more than dangerous. It was treacherous. But without it, their existence would be even more precarious than it was. ‘Sometimes dangers are necessary.’

‘Put dangers aside. Be at ease. Stop your work.’

She turned, then. Gustave was stocky, even for a True Person. A youngster, broad in the shoulders, thick of limb. He had heavy khaki overalls and steel-tipped boots of his own design. He wore his coarse red hair and beard long.

Damona sighed. She’d have to wait for the remains to cool down before she’d be able to investigate properly. ‘How can I save the True People if I stop working?’

‘An honourable goal, eldest.’ Gustave coughed. He shifted, uneasily.

‘What is it?’

He didn’t look at her. ‘An Assembly has been called. You have been summoned.’

Damona sat on the dais at the front of the assembly chamber. She rested her chin in her hand, waited for the rest of the True People to file in. They were old. So few younglings.

She knuckled her brow. Even fewer after Signe died.

It had been a year since her only great-granddaughter had passed. She still mourned.

The Assembly was a shock. She hadn’t heard a thing. No-one had dropped a hint. No-one had muttered a warning in her ear.

I’m getting old, too. She ran her gaze over the crowd. The chamber was filling up, past the fourth set of pillars. Or distracted. Or both.

A distant rumbling. She cocked her head. She took out her pocket watch. It was a sturdy steel model she’d made years ago. She nodded. The noise above was the Circle line train on its way to Cannon Street Station. Right on time.

The assembly chamber was four hundred years old. It was the first large space carved by the True People when they’d congregated under London. It was now at the heart of a complex that had grown into a maze. Families had added chambers, corridors and extensions wherever they were needed. When the Invaders had been digging tunnels for their underground railway it had been a worrying time, but the spaces the True People had opened out were deep. Far deeper than the puny delvings of the Invaders. Their efforts were scratchings and finished far overhead. Noise of the trains reminded the True People that their enemy was close. Damona thought this was a good thing. She didn’t mind the closeness of the Invaders. It meant that none of the True People would forget what they had done.

She climbed to her feet, ignored the twinge from her back. The three hundred True People, the last Neanderthals in the world, hushed.

‘I am Damona,’ she said. Ritual demanded no less. ‘As Eldest, I am your leader. An Assembly has been called. Speak, those who will.’

It was Gustave who stood. Nervous, he was pushed forward by others. He would not meet Damona’s eyes.

‘Eldest,’ he said. Damona saw sweat on his brow. ‘Each of the True People has the right to pursue a life undisturbed by the others.’

‘That is our way. As it has always been.’

‘Except if their life harms another.’

‘Go on.’

‘Your work, Eldest, is dangerous. You have been purchasing materials. You have been contacting the outside world. You jeopardise our security. You cannot continue this without the agreement of the Assembly.’

Murmurs of approval ran through the rows of True People. No animosity, Damona thought, just concern. Gustave stroked his beard, sat down.

Damona let out a long, tired breath. She had led the True People for more than five decades. A hard labour. Individuals never liked being told what to do.

The history of the True People had ever been thus. They united only in extremity. An outside foe, a natural disaster, a threat. Large projects were almost unheard of. Standards meant nothing. It was one of the few things that Damona admired about the Invaders. In their world nails were nails and bricks were bricks, no matter where they were made. For the True People, bricks by different makers were different. Sizes, shapes unlikely to sit together at all.

She had always thought to bring her grand plan to the Assembly. Was it now the time?

She flexed her shoulders. Her right arm hurt after the explosion.

‘Speak!’ someone cried from the back of the chamber. ‘Explain yourself!’

Damona stood. She began by breaking a taboo. ‘The True People are dying,’ she said. Everyone assembled in front of her gasped.

The plight of the True People was never spoken aloud. Everyone knew the truth, but to speak it was forbidden. As if ignoring it would make it go away.

Damona was only stating the obvious. Their numbers had dwindled generation after generation. First they were shunned by the Invaders. Then they were hunted by them. Communities of True People scattered, lost track of each other, falling silent, falling away.

Heads bowed at Damona’s words. Others shrugged and Damona was angered. Apathy was bad. Resignation would only speed their end.

‘Long ago, our ancestors fought the Invaders.’ Her anger rose and she swallowed it. ‘Look at us now. Once we were fierce. We were warriors. Now we go to our doom. Meek. Quiet. Sheep.’

Heads lifted at this. A few angry shouts. Damona was pleased. She would speak truths, here and now, while she still could.

‘Look around you. Has our hiding helped us? Is this the world we deserve, deep underground, huddled like animals?’

A shout came from the rear of the chamber: ‘No!’ Others followed. Support. Damona smiled. She settled. She unclenched fists that had curled tight of their own accord. ‘I have begun a grand enterprise. It is one that will require us all to work together.’

Laughter. Work together? True People? True People worked for themselves, their family!

‘To what end?’ Gustave called out.

‘To save the True People from extinction.’ Damona paused. A great silence filled the chamber. She had them. ‘If we unite, if we dedicate ourselves to my project, we can wipe out the Invaders. We can reclaim the world as our own.’

A low mutter. Growling. Nods. They were with her. Good.

‘We are the supreme artificers,’ she said. ‘We build. We create. We master. We will use our skills to rebuild our world.’

The question came just when Damona wanted it. ‘How?’ Gustave cried.

‘First: we build a better phlogiston extractor. Second: we build a time machine.’

Bewilderment. She went on. ‘We will build a time machine. We will send warriors back to wipe out the ancestors of the Invaders while they are few. They will never grow. Never spread. Never dominate the world. The True People will triumph.’

Damona exulted in the uproar. She hoped her prisoner would hear it. He might tell her what she needed to know.