stood just as the train hit cruising speed, and the three of them rode in silence together, ducking decapitation hazards, the wild shooting past on either side.
Soon the mountains rose into view, their dark bulk a hundred times more ominous now that Aya knew what was inside.
Ren had sent her more math today: Only a mountain could hide a mass driver large enough to hurl a projectile into orbit. Conveniently, the atmosphere was thinner up around mountaintops?less air resistance for the cylinders once they left the shaft. Whoever had built this had thought long and hard about how to destroy the world.
As the dark peaks grew before her, Aya wondered for the first time if mind-rain slammers like the Nameless One were right. Maybe humanity really was too dangerous to be free. It was only three years since the cure, and already someone had built a weapon that would have made the Rusties proud.
At least the discovery made one thing easier: Once they realized what the mass driver was for, the Sly Girls would have to understand that they couldn't keep it secret anymore.
'So what's this theory of yours?' Lai asked.
'Well, it has to do with that stuff.' Aya pointed her flashlight at the hidden door.
Eden Maru was kneeling beside it, the matter hacker in her hands, her fingers jumping across the controls. The tunnel was pitch-black except for Aya's flashlight?the other two had infrared?and the darkness around them came to life as the door began to hum.
'You mean smart matter?' Lai asked.
'Exactly' Aya swept her light across the surface, watching it ripple and undulate, smelling the scent of ram. 'What if those cylinders are laced with it?'
Eden glanced over her shoulder at Lai, but neither said anything.
'That shaft Eden found looks like a mass driver to me,' Aya continued. 'And if the cylinders can change shape, they must be missiles of some kind.'
For a moment there was no sound except the hum of smart matter, then Lai said, 'You mean this whole mountain is a weapon?'
'Exactly. An old-fashioned, Rusty sort of weapon.'
'Interesting theory.' Eden watched the last layers of the door slip aside, revealing the orangey glow of the tunnel. 'How sure are you about this?'
'Almost positive. I can prove it when we get to the cylinders.'
They stepped inside, and Eden turned to close the hidden door again. As expected, Moggle would be trapped on the other side tonight. At least Aya had her spy-cams.
'Clever,' Lai said. 'But you're not the only one who's been clever this week.'
Aya frowned. The two of them didn't even seem surprised. 'This is serious, Lai. Those cylinders could take out a whole city. They're much deadlier than anything used in the Diego War.'
'Maybe so, Nosey. But wait till you see what we've cooked up.'
'But this could mean?' 'Aya, I said wait!'
The door rippled closed, and Aya fell silent. She'd forgotten that Eden Maru was also a tech-head, a much more famous one than Ren. What had she and the Sly Girls been up to for the last week?
The three of them made their way down the stone hallways, through clutter and equipment. When they reached the cylinder room, Aya paused at the top of the stairs, letting her spy-cams take in the ranks of metal missiles.
'What's the matter, Nosey?' Eden said.
'If I can borrow the hacker for a minute, I'll show you something.'
'It's not a toy,' Eden warned.
'I know that. Just let me try something.'
'Let her,' Lai said. 'This could be interesting.'
Eden sighed, then handed Aya the device. It was heavier than it looked, its topside thick with controls and readouts. Ren had warned that it was one of the few machines deliberately designed to be tricky to use?no voice help, no handy instruction screen, as opaque and interface-missing as the Rusty gadgets in the city museum.
Aya made her way down the stairs and chose a cylinder at random. She pulled Ren's memory strip from her pocket and slid it into the hacker's reader.
'You wrote code for a matter hacker?' Eden snorted. 'You're full of hidden talents, aren't you?'
Aya shrugged. She was tired of lying.
The hacker sprang to life, and she pressed it against the smooth metal flank of the cylinder. A hum filled the air, much lower than the sound of the hidden door. Like the rumble of a train approaching, but as smooth as a bow drawing across a cello string.
A scent filled the air. Just like when the door opened, she tasted rain and lightning.
The cylinder began to change, rolling slowly into another shape, like metal syrup poured into an invisible mold. First it transformed into a cone, its point rounded and colored pale white. Ren had said that would happen?the white part was made entirely of smart matter, a heat shield to protect it from burning up on the journey into orbit. Four stubby wings protruded from the sides, one reaching toward Aya like the pseudopod of some metal bacteria.
She stepped back, fascinated by the undulating shapes.
The wings shifted and turned, designed to use the upper atmosphere to guide the missile into the right orbit. Then the transformations came to a halt, like a liquid suddenly freezing in the cold, and the metal sat in front of them unmoving.
Maybe it was waiting for specific instructions, something beyond the simple command Ren had programmed.
'Is that it?' Lai said.
'I guess.' Aya frowned. 'But you saw those wings. That means it's a missile, right?'
Eden smiled. 'That's what we figured. Nice proof of concept, though.'
'You knew?'
Aya cried.
Lai shrugged. 'Once we'd realized the shaft was a mass driver, the rest was obvious. But I'll hand it to you, Aya, we didn't think of testing the cylinders. We were looking at the other half of the equation.'
'What other half?'
'Come and see, Slime Queen.'
Eden took her hand firmly, pulling her toward the entrance to the mass driver. The three of them clambered along the tunnel, through both airlocks, and to the edge of the shaft. Lai pointed down into the blackness.
'Notice anything new?'
Aya?s flashlight faded before it reached the bottom. 'I can't see a thing, Lai. I don't have infrared, remember?'
'Oh, right. Take a closer look then.'
Lai placed one hand firmly in the middle of Aya's back, and pushed her off into the void.
Eden Maru's crash bracelets must have been reprogrammed. They didn't jerk Aya to a halt this time, just slowed her fall, lowering her gently through the darkness.
For a panic-making moment, she wondered if Eden and Lai had discovered what she was, and were planning to leave her down here. Then she heard their giggles following her down the shaft.
'Very funny!' she called up.
Eden drifted past her, saying, 'I hope you're not afraid of falling, Aya. That might be a problem.'
'What's that supposed to mean?'
Eden didn't answer, just grabbed Aya's feet and guided her downward till they settled on a stone floor.
Aya rubbed one sore shoulder, pointing the flashlight with her other hand. The shaft was roomier down here, and a strange contraption stood in the center. It was four long-distance hoverboards crudely bound together with
