About halfway up, Shay reached down to touch her shoulder. "Access hatch."

Tally heard a metal cha-chunk, and blinding light filled the shaft, falling across two hovercraft. In the light they seemed less threatening - dusty and ill-kept, like stuffed predators in some old nature museum.

Shay slipped through the hatch, and Tally scrambled after her, dropping into a narrow hallway.

Her vision adjusted to the orange work lights overhead, her suit shifting to match the pale color of the walls.

The hallway was too narrow for people - hardly wider than Tally's shoulders - and the floor was covered with bar codes, navigation markers for machines. She wondered what nasty contraptions were roaming these halls, searching for intruders.

Shay started up the hallway, waving a finger for Tally to follow.

The hallway soon opened onto a room that was huge -  bigger than a soccer field. It was full of motionless vehicles that towered around them like frozen dinosaurs. Their wheels were as tall as Tally, and their bowed cranes brushed the high ceiling. Lifting claws and giant blades shone dully in the orange work lights.

She wondered why the city would keep a bunch of Rusty construction equipment around. These old machines would only be useful for building beyond the city's magnetic grid, where hoverstruts and lifters wouldn't work. The claws and earthmoving scoops around her were tools for attacking nature, not maintaining the city.

There were no doors, but Shay gestured to a column of metal rungs set into the wall - a ladder leading up and down.

One floor up, they found themselves in a small, crowded room. Floor-to-ceiling shelves were stuffed with a wild assortment of equipment: scuba breathers and night-vision goggles, firefighting canisters and body armor...along with a whole slew of things that Tally didn't recognize.

Shay was already scrabbling through the gear, slipping objects into her sneak suit's pouches. She turned around and tossed something to Tally. It looked like a Halloween mask, with huge googly eyes and a nose like an elephant's trunk. Tally squinted to read the tiny label tied to it: CIRC. 21 CENT.

She puzzled over the words for a moment, then remembered the old-style dating system. This mask was from the Rusties' twenty-first century, a little over three hundred years ago.

This part of the Armory wasn't a storehouse. It was a museum.

But what was this thing? She turned the label over:

BIOWARFARE FILTER MASK, USED

Biowarfare? Used? Tally quickly dropped the mask on the shelf beside her. She saw Shay watching, the shoulders of her suit moving.

Very funny, Shay-la, she thought.

Biological warfare had been one of the Rusties' more brilliant ideas: engineering bacteria and viruses to kill each other. It was about the stupidest kind of weapon you could make, because once the bugs were finished with your enemies, they usually came for you. In fact, the whole Rusty culture had been undone by one artificial oil-eating bacterium.

Tally hoped that whoever ran this museum hadn't left any civilization-ending bugs around.

She crossed the floor, took Shay's shoulder, and hissed, "Cute."

"Yeah, you should have seen your face. Actually, I should have seen your face. Stupid sneak suits."

"Find anything?"

Shay held up a shiny tubelike object. "This should do the job. The label says it works." She slipped it into one of her sneak-suit pouches.

"So what's all that other stuff for?"

"To throw them off the scent. If we only steal one thing, they might figure out what we want it for."

"Oh," Tally whispered. Shay might be making stupid jokes, but her mind was still icy.

"Take these." Shay shoved an armful of objects at her and went back to puzzling over the shelves.

Tally looked down at the jumble of equipment, wondering if any of it was infected with Tally-eating bacteria. She slipped a few pieces that would fit into the sneak suit's carrying pouches.

The largest object looked like some kind of rifle, with a thick barrel and long-range optics. Tally peered down its sight and saw Shay's silhouette in miniature, crosshairs marking where the bullets would hit if she squeezed the trigger. She felt a moment of disgust. The weapon was designed to make any average person into a killing machine, and life and death seemed like a lot to risk on a slip of some random's finger.

Her nerves were jumping. Shay had already found what they needed. It was time to get out of here.

Then Tally realized what was making her nervous. She smelled something through the sneak suit's filter, something human. She took a step toward Shay...

The lights overhead began to flicker, bright white chasing away the room's orange glow, and footsteps clanged from the ladder rungs. Someone was climbing toward the museum.

Shay crouched, rolling onto the lowest shelf beside her, stretching across the jumble of tools.

Tally looked around frantically for a place to hide, then wedged herself into a corner where two shelves didn't quite meet, the rifle hidden behind her. Her sneak suit's scales writhed, trying to fade into the shadows.

Across the room, Shay's suit was sprouting jagged lines to break up her outline. By the time the light steadied overhead, she was almost invisible.

But Tally was not. She looked down at herself. Sneak suits were designed for hiding in complex environments -  jungles and forests and battle-wrecked cities, not in the corners of brightly lit rooms.

But it was too late to find another spot.

A man was stepping off the ladder.

BREAK OUT

He wasn't very scary.

He seemed to be an average late pretty, with the same gray hair and wrinkled hands as Tally's great-grandfathers. His face showed the usual signs of life-extension treatments: crinkly skin around the eyes, and veiny hands.

But he didn't seem calm or wise to Tally, the way crumblies had before she'd become a Special - just old. She realized that she could knock him cold without regret if she had to.

More nervous-making than the crumbly were the three little hovercams that floated above his head. They shadowed him as he strode unseeing past Tally toward one of the shelves. He reached to take something down, and the cameras shifted in the air, zipping in closer, like a rapt audience watching a magician's every movement, always staying focused on his hands. He ignored the cameras, as if he was used to their attentions.

Of course, Tally thought. The hovercams were part of the building's security system, but they weren't looking for intruders. They were designed to watch the staff, making sure nobody snuck off with any of the horrible old weapons stored here. They glided smoothly over his head, watching everything this historian - or museum curator, or whatever he was - did here in the Armory.

Tally relaxed a little. Some crumbly boffin who himself was under guard was a lot less threatening than the squad of Specials she'd been expecting.

He handled the objects delicately, and the care he took with them made her vaguely nauseous, as if he saw them as valuable works of art instead of killing machines.

Then suddenly the crumbly froze, a frown on his face. He checked a glowing palmbook in his hand, then started sifting through the objects one by one...

He'd noticed something missing.

Tally wondered if it was the rifle poking into her back. But it couldn't be: Shay had taken the weapon from the other side of the museum.

But then he picked up the biowarfare filter mask. Tally swallowed - she'd put it back in the wrong place.

His eyes slowly swept the room.

Somehow, he didn't see Tally wedged into her corner. The sneak suit must have melded her outline into the shadows on the wall, like an insect against a tree limb.

He carried the mask over to where Shay was hidden, his knees centimeters from her face. Tally was certain he'd notice all the objects she'd borrowed, but once the crumbly had put the mask back in its proper place, he nodded and turned around, a satisfied expression on his face.

Tally breathed a slow sigh of relief.

Then she saw the hovercam staring down at her.

It still floated just above the crumbly's head, but its little lens was no longer watching him. Either Tally's imagination was running wild, or it was pointed straight at her, slowly focusing and refocusing.

The crumbly walked back to where he'd started, but the camera stayed where it was, no longer interested in him. It drifted closer to Tally flitting back and forth, like some hummingbird unsure about a flower. The old man didn't notice its nervous little dance, but Tally's heart was pounding, her vision blurring as she struggled not to breathe.

The camera flew still closer, and past its flitting eye Tally saw Shay's form shifting. She'd also seen the little hovercam - things were about to get very tricky.

The camera stared at Tally, still unsure. Was it smart enough to know about sneak suits? Would it just chalk her up to a smudge on its lens?

Apparently, Shay wasn't waiting to find out. Her suit's camouflage had changed into the sleek black of armor. She pulled herself silently out into the open, pointed at the camera, and drew her finger across her throat.

Tally knew what she had to do.

In a single motion, she whipped the rifle from behind her back. It struck the hovercam with a crack, sending it flying across the museum, past the astonished crumbly's head, and careening into a wall.

It dropped to the floor, stone-cold dead.

Instantly, a screaming alarm filled the room.

Shay burst into motion, running toward the ladder. Tally squeezed out of her corner and followed, ignoring the astonished crumbly's cries. But as Shay jumped for the ladder, a metal sheath snapped shut around it. She bounced back with a hollow clang, her suit cycling through a sequence of random colors from the impact.

Tally swept her eyes around the museum - there was no other way out.

One of the two remaining hovercams buzzed straight up to her face, and she smashed it with another blow from the rifle butt. She swung at the other one, but it shot away into a corner of the ceiling, like a nervous housefly trying not to get swatted.

"What are you doing here?" the crumbly shouted.

Shay ignored him, gesturing at the remaining hovercam. "Kill that!" she ordered, her voice distorted by the sneak suit's mask, then spun back toward the shelves, riffling through them as fast as she could.

Tally grabbed the heaviest-looking object she could find - some sort of power hammer - and took aim. The camera was flitting back and forth in a panic, swinging its lens one way and then the other, trying to keep track of both her and Shay. Tally took a deep breath, watching the pattern of its movements for a moment, her mind racing through calculations...

The next time the hovercam's lens left her for Shay, she threw.

The hammer hit the camera dead center, and it dropped to the floor, sputtering like a dying bird.

The crumbly jumped away from it, as if a wounded hovercam were the most dangerous thing in this museum of horrors.

"Be careful!" he shrieked. "Don't you know where you are? This place is deadly!"

"No kidding," Tally said, looking down at the rifle. Was it powerful enough to cut through metal?

She took aim at the sheath that had covered the ladder, braced herself, and pulled the trigger...

It made a clicking sound.

Bubblehead, thought Tally. No one kept loaded guns in a museum. She wondered how long it would be before the ladder would open back up to reveal one of the evil machines from the shaft, fully awake and primed to kill.

Shay knelt in the middle of the museum, a small ceramic bottle clutched in her hands. She placed it on the floor and grabbed the rifle from Tally, lifting it over her head.

"No!" the crumbly cried as the rifle butt swung down, hitting the bottle with a dull thud. Shay raised the weapon for another swing.

"Are you crazy?" the crumbly yelled. "Do you know what that is?"

"Actually, I do," Shay said, and Tally could hear the smirk in her voice. The bottle was making its own beeping noise, the little red warning light on it flashing furiously.