As I leaned down and disabled the security devices around the small grate, I felt Bex watching over my shoulder.

"I always thought the elevators to Sublevel Two put us somewhere over there." She pointed in the opposite direction. I smiled up at her. "But we're not going to the elevators, are we?"

At precisely 0147, The Operatives tested their theory that the mirrors in the new compacts from McHenry Cosmetics are the appropriate sixe to slide over and deflect the laser beams that cover the opening of all ventilation points.

(The Operatives were correct.)

At precisely 0207, The Operatives tested the new Electromagnetic Signal Reallocator (Official Name and Patent Pending) that Operative Sutton had developed for the occasion.

(It was successful.)

At precisely 0208, Operative Baxter said a prayer. And jumped.

The airshaft was small. Crazy small. I'm-really-glad-I-skipped-dinner-after-all small.

There was no way a grown man could have fit. It was an entrance that was only suitable for a girl. A Gallagher Girl, I thought as I slid down the cable like it was a fireman's pole, the clamp in my hand growing hot, searing into my gloves as I zoomed into the depths of the ground.

I knew Bex was below me, but I couldn't see a thing, Macey and Liz were above me, and I hoped that was why I couldn't see even the faintest hint of light above me as I hurtled into what felt like the world's tiniest volcano.

Deeper and deeper I went. Faster and faster I fell. I felt the air rushing past me, my hair blowing away from my face, the cable burning hotter in my hands until . . .

"Look out!" Bex yelled, as suddenly I broke free of the shaft. My arms felt as if they might pop out of their sockets when I squeezed the clamp and slammed to an almost instantaneous stop. I was dangling from the cable, looking down into the cavernous space of Sublevel Two.

"I can't believe that worked," I admitted, breathless.

"Cam!" Bex shouted, stopping me before I could release my hold on the cable. "Don't.

Move. A muscles."

We were suspended thirty feet above the hard stone floor of a room that, despite a semester of studying in Sublevel Two, I'd never seen before. The subs are a vast and winding maze of classrooms and offices, resources libraries and storage for some of the covert world's most highly classified secrets. And right then, Bex and I were looking through the dim glow of security lights at a massive room filled with hundreds of shelves and filing cabinets, a complex system of wiring and explosives . . .

And the most complex laser grid system I had ever seen.

"So," Bex said, smiling up at me through the pulsing glow of the emergency floodlamps,

"wanna hang out?"

A moment later, the vibrations on the cable grew stronger, and I looked up in time to see Liz hurtling toward me through the air, stopping just above me.

Macey was close behind and out of breath as she asked, "What if all this?"

Bex and I looked down at the rows of top secret information and the high-grade explosives that ran the length of the room, neither of us able to hide the awe in our voices. "It's a burn bag," we said in unison.

"What's that?" Macey asked.

"It's the stuff that can't fall into the wrong hands. Ever. It's the stuff that rigged to blow up in case . . . in case the worst happens."

Which was true. But scary. Because at that moment, technically, that worst that could happen was us.

Bex was the first to drop to the floor, nimble as a cat, landing between the red beams, then flipping and jumping through the air, navigating her way to the small panel on the side of the room. It if hadn't been so utterly terrifying, it would have been beautiful. Like ballet. But with a way higher casualty rate.

"Now, Liz," she yelled, and Liz pulled out her crossbow and took aim at the wall six inches above Bex's head.

"Uh . . . Liz . . ." Macey started.

"Sorry," Liz said, and raised her aim about a foot.

I don't think any of us could draw a breath as the arrow sailed through the air, a small cable trailing behind it, then landed perfectly just above the panel on the wall.

"Awesome," I said. "Now, just like we practiced - take the extra clip on your harness and put it on Bex's cable. Yeah. Just like that. You're doing -"

"Whoopsie daisy."

And that's when Elizabeth Sutton, supergenius, forgot that her bag was unzipped and let her Advanced Encryption textbook fall, end-over-end, into the heart of the laser field below.

"Liz!" I yelled, but it was too late. Lights began to pulse. Below us, the lasers began to move, red lines snaking over the ground, and I realized our only option.

"What do we do?" Macey yelled.

"We run!"

As we dropped to the ground, I couldn't hear my own thoughts - much less the footsteps of the girls who ran beside me. Red lights swirled. Sirens screamed. It was as if Sublevel Two were burning as Liz carried her laptop to where Bex stood waiting by the electronic nerve center that controlled all of Sublevel Two's modern defenses.

But modern . . . yeah, modern was the least of our problems.

At the far end of the room, there was a massive window made of stained glass. For a second I stood there, wondering why anyone would install a window in an underground room. It would have been far more weird and way less terrifying if the space behind the glass hadn't been quickly filling up with water.

"So that coming from . . ." Macey started.

"The lake."

"Sp if we don't stop this . . ." she started again.

"We drown," I said, but Macey was already gone - sprinting across the room.

"What do we do?" she cried. She was searching the walls, pushing on stones - frantically looking for a way to make the water stop rising. "Where's the switch? I thought Mr.

Solomon told Zach there was a way to turn it off."

As the water rose, the stained glass seemed to sparkle. The light looked different the higher the water went, and I couldn't help but remember the very first assignment Joe Solomon had ever given me: notice things.

"I've seen this before," I said, still staring at the familiar images in the glass - brightly colored shapes and lines. "Macey, have you seen it before?"

"Sorry, Cam," she said, still searching. "I'm a little busy here."

"it's like the one upstairs. You know, the big one? Except . . . it's different. It's almost like

. . ." I trailed off. My voice caught. And I knew when we had to do. "It's not a window -

it's a puzzle!"

The glass was cold to the touch when I reached for it. The device was at least a hundred years old, and when I pushed on a deep blue section of glass, at first it didn't budge, and I thought I was wrong. But I pushed harder and . . . movement. The window was like a kaleidoscope, a moving, swirling mass of glass and hidden gears as I slid the blue section smoothly into place in the center of the massive frame.

"Macey, help me," I said, and together we went to work, our eyes and hands feverishly flying over the window's hundreds of sections as quickly and deftly as we could, trying to duplicate the upstairs window that I had never truly looked at until Joe Solomon came into our school.

All around us, though, the sirens kept blaring. The lights kept swirling. And, worst of all, the water kept rising.

"Lizzie?" I heard Bex yell behind me.

"Almost . . ." Liz said, her fingers flying over the laptop's keys. "Almost . . . got it!"

Instantly, the sirens went silent. The lights stopped swirling. From the corner of my eye, I saw Liz and Bex give each other a high five, but the water level kept rising.

I thought of what Mr. Mosckowitz had told Agent Townsend that night in the shadowy halls - that every generation had added a layer of defense to that honored place - and I knew that the original Gallagher Girls were in many ways the wisest.

"Got it!" Macey, yelled, pushing the final piece into place, but nothing happened.

It felt like an eternity before a shrill mechanical voice sounded through the echoing space. "IDENTIFY. IDENTIFY. IDENTIFY. WHO GOES THERE?" it asked.

And then instinct must have taken hold, because the four of us shouted the first words that came to mind : "We are the sisters Gillian!"

I held my breath and said a prayer until the water began to recede and the mechanical voice said, "WELCOME HOME."

Chapter Thirty

There are things people like Townsend would never understand about the Gallagher Academy. Ever. You see, it isn't about a Gallagher Girls - it's about being one of the Gallagher Girls. Plural. All of us. Without Bex, I would have triggered the sensors.

Without Macey, I might never have solved the puzzle in time. And without Liz . . . well, Liz had multiple roles on this particular mission.

"How high is that again?" she said as she walked beside me.

"Not that high," I said slowly, looking up at the towering shelves that lined the walls of Sublevel Two.

It wasn't where we stored the chemicals. As I looked around the long rows of tall shelves, there wasn't single weapon in sight. But the information contained within this room was volatile enough to bring my school crashing down, potent enough to poison every member of our sisterhood. And I knew we didn't dare stay too long - that we live our lives on a need-to-know-basis for reason.

Unfortunately, I was the only one who felt that way.

"Ooh! Cool!" I heard Macey cry from one row away, despite that fact that, upstairs, half of the Gallagher Academy security team was now on high alert, wondering what in the world had just happened in Sublevel Two.

"Hey, Cam," Bex called, "did you know Amelia Earhart spent the last twenty years of her life undercover in Istanbul?"

A half second later, Macey came running around the end of an aisle, a file in her hands.

"Quick, guys, I've for pictures of Professor Buckingham . . . in World War Two . . . in a swimsuit!"

Bex raced to look at the images, but my gaze was locked on Liz as I ran a cable through the utility belt that hung around her tiny waist.

"Liz, this is silly. I'll do it," I told her.

"But Cammie, Zach said it's in the very middle of the highest shelf. It's going to be really hard to get someone in exactly the right place, and I'm the lightest," she said, citing the one scientifically verifiable - and thus relevant - piece of information we had.

"You don't have to prove anything, Lizzie. I can -"

"They need you, Cammie," she said, her voice no louder than a whisper. "And if their side needs you alive . . . our side needs you alive." She looked up at the tall shelves and took a deep breath as if clearing all those unpleasant thoughts away and focusing on a single, quantifiable fact: "I'm the lightest."

"Bex, we're ready," I called out. A second later she appeared, Liz's crossbow in her hands. It looked absolutely effortless as she took aim at the ceiling fifty feet overhead. I heard a cable whirling, watched the coil at my feet slowly disappear, until I heard the metallic noise that titanium makes when it strike soild stone.

"Ready?" I asked Liz, who nodded.

"You can do it," I silently whispered while Bex grasp the other end of the cable and pulled. In the next moment, Liz was floating gracefully (or as gracefully as Liz does anything) over the shelves marked: WARNING, HIGH VOLTAGE.