And then I broke away. "So," I asked, as if I got kissed like that all the time (which, believe me, I don't), "where is it you're taking me again?"

"The tombs."

Chapter Thirty-Eight

In the next twenty minutes, I broke maybe a dozen rules of covert operations.

After all, I didn't know where we were going. I had no idea what we were going to find when we got there. I hadn't planned alternate entry strategies, exit strategies, or strategies for keeping my ponytail from blowing in my face. All I knew for certain was that Zach's hand was gripping mine (despite verifiable research that people are way stealthier when holding on to nothing), and that Bex's voice was the only familiar thing I could hear.

"Chameleon, what did he say again?" she asked through the comms unit in my ear as Zach and I covered the open ground beyond the ridge at a full run. "Because we're searching the database for 'tombs,' but -"

"It's not in the database," Zach cut in.

"Is it some kind of cemetery? We can't find an entrance on the -"

"There are no recorded entrances."

"Or references to it anywhere," Bex finished.

Zach looked at me. "It's not the kind of place that gets referenced."

"Cameras passing in three, two, drop!" Liz commanded from her watch post, and Zach and I fell to the ground like stones.

"Roll," Liz said, and I propelled myself down a steep incline and landed in a muddy ditch.

I heard voices coming from above us, footsteps as the Blackthorne Boys ran past in perfect unison, while Zach and I continued crawling through the mud.

"Wait, it's not an actual tomb, is it?" Macey asked. It seemed like an excellent question, but Zach was silent, still crawling away from the buildings and the guards, and toward the mountain that formed the backdrop of the school.

"What are the tombs, Zach?" I asked again when we reached the base of the first hill and climbed out of the ditch and into the shelter of the trees. The ground was rough and steep.

We walked along a path that was overgrown with weeds and brush - as if the wilderness were trying to reclaim it.

"Guys, you're clear now," Liz said from two miles away, but I'd already sensed it.

The marching boys were gone. No cameras could possibly reach us through the dense canopy of trees.

Only a single ray of moonlight sliced through the limbs. I remember that now - how I could so plainly see the features of Zach's face, the look in his eyes as he started pushing aside the moss-covered rocks that sat on the steep mountainside.

"What are you looking for?"

"There should be an entrance around here somewhere." He kicked at the dead leaves and fallen brush that covered the forest floor. "It'll be hidden - made to blend in. but there should be a switch, or maybe . . ."

"A lever?" I asked, walking three feet to a tree that grew from the steep mountainside at an angle unlike any of the others. I reached for the only limb in the entire forest that didn't have a single new leave. "You mean like this one?"

"Caves?" I heard my own voice echo, even though the word had been barely louder than a whisper. "The tombs are caves?"

"Watch your step," was Zach's answer.

I could still hear my roommates chattering in my ear, but the sound dissolved deeper into static with every step behind the hidden door.

The stone walls around us were close and damp, lit by bare, dim bulbs that hung at regular intervals. I had a feeling that we weren't going underground. It was more like we were going straight through the mountains that were the Blackthorne Institute's first and perhaps best line of defense.

"The Native Americans indigenous to this area used to bury their dead in caves like this,"

Zach offered out of the blue. "That's why they call them the tombs. The army used this whole area for weapons testing and training in World War Two. After the war, they found another use for it."

It was strange hearing Zach offer up anything about his past. I wanted to asked for more, but stayed quiet, remembering summers on the ranch and how the baby calves would creep close sometimes, curious and timid, uncertain whom to trust. I knew if I moved too fast I might scare him away, so I just waited.

"We don't really . . ." He looked at me. "We don't really use them anymore."

"How far do they go?" I asked, mesmerized.

"Far."

"How many branches and offshoots are there?"

"A lot."

"Are you going to tell me why you were so desperate to keep me out of here?" I asked.

He stopped suddenly, and I ran into his chest. It was almost as hard as the stone walls around us.

"You'll see for yourself soon enough."

We walked for what felt like hours, disabling booby traps and dodging surveillance cameras.

"Maybe we should split up," I suggested.

"You stay with me," Zach said, like it wasn't really up for debate The passageway was taller than the ones at the Gallagher Academy. The concrete walls felt more modern. It was a next-generation tunnel, to be sure, but it wasn't new or nice.

Nothing about it was anything but functional, and the dank smell and thick cobwebs told me that it hadn't really functioned in a very long time.

"Watch your step," Zach warned when we reached a sloping portion of the tunnel where water congealed in thick black pools.

"Oh, I bet you say that to all the girls you bring down here."

Zach stopped. When he turned, he didn't even look like the boy I knew. " No one comes down here."

Five feet ahead, the stone passageway widened. The ceilings rose taller. I could hear the steady drip, drip, drip of water seeping through the cracks in the stone above us and falling into puddles on a concrete floor. But there were no soft edges there, no bright lights. Stepping inside, I realized that we have our fair share of secret underground chambers at the Gallagher Academy, but I had never been anyplace like this.

Chains dangled from the tall ceilings along one wall. A collection of dummies with crude red circles painted on their chests lined another. Stainless-steel tables stood in the middle of the room while cobweb-covered trays with syringes and pliers sat waiting, as if someone might walk in at any moment, brush aside the dust, and continued with some terrible experiment.

"We don't use it anymore," Zach said, his voice soft despite the fact that there wasn't a soul who could have overheard us. Shame seeped into his words as he looked at the damp concrete floor. "We really don't use it anymore."

A half dozen other passageways opened into this room, and yet I felt the mountain pressing down on me as if there were no way out.

"Zach . . ." My voice caught in my throat. "What is this place?"

"You really don't know what kind of school this is, do you?"

"It's a spy school," I snapped, blood pounding in my veins.

He shook his head slowly. Even in the dim light I saw his eyes go wide. "Not spies. Not always."

"Then what?"

"Come on, Gallagher Girl - a school in the middle of nowhere for troubled boys with no other place to go? You know what this place is."

I looked at the room around us, thought about the rifle ranges and marching boys, about the hours my roommates and I had spent last spring searching for any clues about Blackthorne and finding nothing but secrets and lies.

"No," I said. "Mr. Solomon went here. He -"

"Was starting to change things," Zach finished. He stepped closer. "You know what we are, Gallagher Girl."

"No." I shook my head. "You can't be . . ."

There are a lot of terms for what Zach was trying to say. Killers. Wet work artists. But all I could do was look at the boy who stood beside me - the boy I barely knew - and whisper, " Assassins."

"I told you this place was made to prepare for war - World War Two, the Cold War, and all the wars that could have happened but didn't. Or haven't yet." He stared at me, almost pleading as he whispered, "We don't use it anymore."

"Is this why they don't trust you? The Baxters . . . Aunt Abby -"

"Are smart people with good instincts." He looked away, then back again.

"But that doesn't make any sense, Zach. You didn't build this place. What could you have possibly done that is so terrible?"

"No!" Standing there, hundreds of feet into the mountain, there was no way to know how far the shout reverberated through the maze of stone.

"Really. You can tell me."

"No. I really can't."

Upon leaning the original purpose of the Blackthorne Institute for Boys, The operative thought she might more easily understand the Asset.

(But it turns out, potential future assassin-slash-spy boys are the most confusing boys of all.)

It took another hour to reach it. Twice we found the tunnels blocked by a cave-in, a hundred tons of stone standing in our way. Once, Zach admitted we were on the wrong path, and we had to backtrack a hundred yards. We passed three more rooms like the first we'd seen - a dozen locked doorways and concrete bunkers so dark I couldn't see a thing.

"I've never been this deep," he admitted. Somehow, I knew exactly how he felt.

"Not to sound ungrateful or anything, but do you know where we're going?"

He smiled for what felt like the first time in hours. "Not exactly." He reached for my hand, bent to ease beneath a low-hanging arch. "Joe told me where he left it, just in case . . . in case of this."

"And where's that?" I asked, but Zach stopped.

He pointed. "In there."

The room was large - two stories tall with a t least a half dozen tunnels spiraling off of it.

Somehow, just standing there, I knew we'd finally reached the center of the mountain.

As Zach and I stepped onto a small metal landing on the second story, I looked down on the room below us. It was crude and basic. Metal stairs ran down to the lower floor.

Shelves and filings cabinets lined the walls. And on every inch of surface there were files and boxes and relics of the past.

"It's . . ." Zach started slowly. "It's sort of like Blackthorne's version of Sublevel Two."

I followed him down the stairs and watched him go to the far side of the room and squat down beside a rusty shelf. I held my breath as he reached, stretching as far as he could, then pulled out a spiral notebook wrapped tightly in plastic.

"That's it?" I asked. It looked so plain - like a million other notebooks carried by a million other kids. Finally, I truly understood the fact I'd known for months: Joe Solomon had been sixteen.

Zach tucked the journal into his belt and under his jacket, then took my hand. Wordlessly, we climbed the metal stairs and started back down the tunnel from which we'd come.

It seemed so easy. Our mission was over. We'd won.

But that was when we heard the voices.

Chapter Thirty-Nine

My first thought was that the Blackthorne security team had found us - that we'd missed a motion sensor or tripped a silent alarm - and I started preparing my excuses . . . Zach was my boyfriend. I was there on a dare. Breaking into Blackthorne was the best extra credit project ever!

But then Zach and I dropped to our stomachs and crawled back to the metal landing that overlooked the massive storage space below, and . . .