Eventually it grew bright enough that I shut my flashlight off. Soon after that the tunnel opened out into a small chamber, just large enough for the three of us to stand in. Through a narrow slit at the far end we could see there was a much larger chamber beyond, and the light seemed to be coming from there.

Slowly, warily, we approached that final opening, and for a moment we all stood as still as the rock itself, listening for any sign of danger. But all we could hear was the distant drip of water, the music of a living cave. So I took the lead and squeezed through the narrow slit.

I emerged into a ma.s.sive chamber. I didn't need a guidebook to tell me that this was the crown jewel of Mystic Caverns, the point where all tours converged. The ceiling was so far overhead I couldn't make out its limits, and a thick forest of columns and stalagmites surrounded me, making it hard to see what else was in the chamber. All about the room, inside crevices and behind formations, the light cast deep black shadows. G.o.d alone knew what might be hiding in any one of them.

As I crept warily forward I thought I could make out a large open area ahead of us, surrounded by a waist-high railing. The light we'd detected was coming from a series of lamps affixed to its support posts, and though the illumination must have been pretty dim by aboveground standards, it was nigh on blinding to us in our current state. I blinked as tiny purple spots swam before my eyes, as my eyes slowly adjusted. Then I got to where I could see what was in the central part of the chamber. And I froze.

Rita came up behind me. I heard her gasp.

Facing us was an arch. It was twice as tall as Devon and wide enough that he could not have touched both sides at once. The underlying shape of it was perfectly regular, but its surface was coated with flower-like cl.u.s.ters of cave crystals-anthodites-some of them so tiny I could hardly make out their details, others more than a foot long. The needle-like blossoms glittered as we shifted position, crystalline spines seeming to shift and sway as if they were living things.

The caverns hadn't made this thing. Nor had human hands. It was . . . unearthly.

Beside the arch was a row of steel tables on wheels, the kind you might see in a morgue. Atop each one was a white sheet draped over what appeared to be a human body. I was about to move toward them when suddenly there was a loud metallic sound from the far end of the chamber. The lamps flared to sudden brightness, blinding us. From behind we could hear a large metal thing approaching . . . or maybe human feet pounding on metal.

"Hide!" Devon whispered fiercely.

As if we needed to be told that.

I looked about feverishly for cover and spotted a broad column near our entrance point that looked wide enough to hide behind. Fear lent fire to my muscles as I sprinted toward it. Rita and Devon ran off in other directions, presumably toward hiding places of their own. There were certainly enough of them in the chamber.

I dove into a thick black shadow behind the column, and I prayed that no one entering the main chamber would be able to see me. I leaned back against the wet rock and tried to stay calm, my heart pounding so hard I thought it would burst out of my chest. The metallic sounds were louder now, and yes, they clearly were footsteps. Curiosity warred with fear in my heart, and after a brief stalemate the former won out by a narrow margin; I peeked gingerly around the edge of the column to see who was coming.

In our fixation on the crystal arch we hadn't noticed a suspended walkway leading away from the far end of the chamber. I could see two figures there, talking to one another as they walked along the metal grate toward us. On the left was a woman dressed in a navy skirt-and-jacket ensemble, a neat and conservative figure with hair coiffed to meticulous perfection. The other figure was thinner and taller, and the voice sounded male, but I couldn't get a clear view of him.

"We don't have the facilities for this," the woman was saying. Her accent reflected the same odd cultural mix as that of my brother's kidnappers, and she was clearly annoyed. "This party should have been broken up into two. At least."

"This is the way the Shadows want it done, so this is the way it will be done." The man's voice was quiet, resigned. "Arguing with them is a bad career move, Delilah."

She snorted lightly. The sound was derisive and delicate at the same time, and I got the impression it was something she'd rehea.r.s.ed. "We wouldn't be in the mess we're in now if they would let the other Guilds counsel them."

"I strongly suggest you don't let them hear you say that."

"Of course, Malik. I'm not a fool. But they're not here right now, are they?"

Then they pa.s.sed out of sight behind the column. I inched my way around the back of it, seeking a safe vantage point on the other side.

"Are you sure of that?" the man said.

"Please. I can smell their undead presence from two spheres away. Maybe you've been around them too much if you can't."

If the man responded, I didn't hear it. The woman's words rang in my head, sending a wave of fear up my spine. No other focus was possible.

I can smell their undead presence.

For all our nervous banter about aliens and changelings and animal-controlling powers, I knew in that moment that I hadn't believed any of it. Deep in my heart I'd clung to the belief that there was a rational explanation for everything we'd seen, and if we just looked in the right places and asked the right questions we would figure it out. That was why we'd come down into the caverns, right? To search for rational explanations.

I can smell their undead presence from two spheres away.

Maybe this was all a dream. Maybe I'd wake up soon, and I'd go into Tommy's room and tell him all about it, and we'd have a good laugh together about how crazy my dreams were.

When the voices were audible once more, it sounded like the man was near the crystal arch. "Given how many people will be coming through today, you might want to stand back a bit."

Heart pounding wildly, I dared another peek around the edge of the column. The two of them were in front of the arch, waiting silently and expectantly for . . . what? I could see the man more clearly now. His skin was a mottled grey, the same color as the stone behind him. His eyes were large and dark and the outer corners were angled slightly upward, like a cat's. His clothing was normal enough, but all of it was the same shade of grey as his skin, which made it hard to pick him out from the limestone background. I couldn't tell if he was the same person who had carried Tommy out of our house or not, but he was definitely of the same type.

Then the archway began to glow. I pressed back into the shadows as far as I could without losing sight of it. I had the impression of a complex geometric design filling its interior, though it wasn't something I saw, exactly, more like something that I knew in my gut was there, even though there was no visible evidence of it.

A man stepped through the arch.

His face was pale, and it had an unnatural sheen to it. His body was solid enough in the center but its edges looked strangely insubstantial, as if someone had begun to erase him. Wisps of shadowy mist played about him, and for a moment it looked as if they were about to coalesce into some sort of creature-or creatures-but instead they faded into nothingness before any features became recognizable. The long grey robe that he wore lent him a vaguely medieval air, a jarring contrast to the very modern clipboard he was carrying. For some reason that last item made him seem even creepier.

He took a few steps away from the arch, looked down at his clipboard, and started to read. His voice was a thin tenor that sounded . . . empty.

"Arianna Withersham, Apprentice of Elementals. Naomi Balfort, Master of Weavers. Nicholas Tull, Journeyman of Seers." He recited maybe eight names in all, each with a t.i.tle.

The grey man, meanwhile, had pulled out a smartphone and was checking those names against a list of his own. He nodded his approval as each name was spoken, and when the recital was done he said "Good to go," and gestured toward the row of gurneys.

The man with the clipboard looked around the chamber, and I realized with a start that he was about to turn in my direction. I fell back into the shadows as quickly as I could, nearly slipping on the wet floor in my haste. My heart almost stopped. Oh G.o.d, please don't let him see me! I couldn't even imagine what would happen if these people realized I was in the room spying on them.

One second pa.s.sed. Two. In all my life I've never felt time move as slowly as it did at that moment.

Then I heard the sound of gurneys being wheeled across the stone floor. People walking back and forth. Suddenly there seemed to be many more people than had been there a moment before. I heard a lot of voices, mostly young, murmuring and laughing in the quiet way that students do when cla.s.s is about to begin.

The woman in the suit started speaking, and all the other voices subsided. "Ladies and Gentlemen, Masters and Apprentices, Journeymen and Aspirants: welcome to Terra Colonna. My name is Delilah Mason, and I will be your docent for this visit. If you would all be so good as to follow me, I will see to your orientation."

I could hear a number of people follow the sharp click of her heels as they moved across the room; the steel walkway thrummed as they stepped onto it one by one, their footsteps becoming less and less audible as they moved away from the main chamber. There was a bit of giggling in the distance, and then they were gone.

The grey man said quietly, "You said there would be fourteen."

"The others were delayed." The voice of his pale companion sent shivers up my spine.

"I have a schedule to keep. When are they expected?"

"Half an hour."

I heard a sigh of exasperation. "What about the Drake boy? Did he make it through all right?"

I felt my heart lurch in my chest.

"He arrived intact and in the right time sequence. But I'm told the exchange wasn't well balanced. If he ever attempts to return home there could be consequences."

"Well. That's not going to be an issue, is it?"

Silence.

"What do the Shadows want with him, anyway?"

Silence.

The grey man snorted. "All right. Have it your way. I'll return in half an hour. Make sure the transfers are ready by then."

I heard someone leave the chamber. A moment later the strange geometric vision flared again, then faded, dissipating like golden smoke.

And they were gone.

I leaned back against the column, heart pounding, struggling to make some kind of sense of what I'd just heard. It sounded like my brother was still alive, so there was still hope. But why had they taken him?

"Jesse!" The call was only whispered, but the place was like an echo chamber, magnifying the sound.

I peeked out from around the column, and saw Rita and Devon standing out in the open. After a brief glance around the place to see for myself that the visitors were really gone, I joined them.

For a moment we just stared at each other in silence.

"How much did you see?" Devon said at last. I could hear in his voice how hard he was struggling to stay calm.

I drew in a shaky breath. "The grey guy and the woman. And that undead thing, that came through the arch."

"I saw people come through it." Rita's voice was a haunted whisper. "The grey man pushed a trolley through the archway each time one of them arrived, and it . . ." she drew in a deep breath, "it disappeared."

"The timing of it seemed important," Devon added.

A balanced exchange, I remembered.

I walked over to the nearest gurney, paused for a moment to gather my courage, then folded the top of the sheet back to see what was underneath.

The body on the steel surface was that of a teenage boy. He looked dead, but when I put my hand on his cheek I could feel living warmth. So I took out my phone and held the screen to his lips. There was no fog from his breath, or any other sign of life.

Devon and Rita uncovered the other bodies. Two adults and four teens. Most of them looked as if they were sleeping peacefully, until you noticed they weren't breathing. One of them was a girl exactly my age; seeing her lying there like that made me queasy.

"Caucasian male, 43," Rita was reading from a form clipped to the end of one of the carts. "Blood type A+, 180 pounds, muscle tone 6. Single, no offspring, no siblings. Diabetes, allergy to dust mites. College professor. Musical talent." She raised an eyebrow. "Conservative Republican."

"Creepier and creepier," Devon muttered.

Rita looked at me. "The Drake boy they were talking about. That's your brother?"

Lips tight, I nodded.

Soon the grey man and his pale companion would return. More people would emerge from the crystal arch, ready to tour Terra Colonna. Our world. And meanwhile these unconscious bodies would be exchanged for them, and transported to . . . where?

Wherever my brother is, I thought. A tremor of fear ran up my spine.

"They came this way," I murmured. "The ones who are hunting us. The ones who burned my house to the ground, trying to kill me. This is how they got here."

And this is how they will go home.

I walked over to the body that looked so much like mine. In a short while this girl would be wheeled through that portal, into another world. A place where alien-looking grey men and undead tour guides-and G.o.d alone knew what other kinds of monsters-took little boys prisoners. A place where my death, and many other deaths, had been planned.

There comes a point when so many crazy things have happened that your mind just can't process them any more. Insane things start to sound reasonable.

"We could go there," I said quietly. I put my hand to the girl's cheek. It was warm, so warm.

"You mean . . . take their place?" Rita clearly thought I had gone insane.

"You said the exchange was one-for-one. We know more visitors are about to arrive." I paused. "They'll send these bodies through to the other side, won't they?"

"Jesse . . ." From her tone of voice you could tell she thought she was arguing with a crazy person. "We don't have a clue what's out there."

"No," I said softly. "We don't. But we know what's here." I indicated the bodies. "And when will we have a chance like this again? Maybe never."

And what about these people? an inner voice demanded. Where will you hide them while you make your subst.i.tution? And what will happen to them once you're gone?

I looked down at the girl on the table. So still, so helpless. But she wasn't hooked up to any kind of machine or IV, I noted. Which meant that whatever strange suspended animation state she was in, removing her from the gurney wasn't likely to make a difference. We could hide her body behind one of the formations, where people pa.s.sing through the crystal arch were unlikely to see her. Later on, when the aliens who ran this place discovered our empty gurneys on the other side of the arch and realized what we'd done, they would find her.

And then what?

My brother is gone, I told myself. How else can we find him, if we don't do this?

Devon put a hand on my shoulder; I could tell from his expression that the same thoughts had been running though his mind. "We could call in some outside help," he said quietly. "Now that we know there's stuff down here for them to see. There are people far better equipped than we are to figure all this out."

"And what will happen when they get here?" I demanded, turning on him. "They'll cordon this place off. Seal all the entrances, station guards outside, do whatever it takes to keep the public from ever finding out about this place. Then the government will bring in its scientists, and they'll study this arch molecule by molecule, write papers about it and conduct experiments and hold conferences and maybe, after years of that, start sending people through. One lost boy will be the least of their concerns." I shook my head. "You think we'll be able to sneak down here again, once that starts? We'll lose access to this place. Forever. A sacrifice to science, nothing more."

Devon said nothing, but I could see the uncertainty in his eyes. I couldn't read Rita at all.

"Aren't you the least bit curious?" I asked her. "Don't you want to know what's out there?" I looked back at Devon. "Don't you want to be the one who discovers a new world? Instead of reading about how someone else did it?" I was trying desperately to appeal to the science geek in him. Devon was the practical one, always thinking ahead. The guy who had thought to make chalk marks so we could find our way home. If I was going to dive headfirst into an unknown world, I definitely wanted him with me.

But to my surprise it was Rita who spoke first. "c.r.a.p," she muttered. "I've got nowhere better to go."

I looked at Devon. Still he said nothing.

"We left notes at your house," I pressed. "If we don't come back in the next few days our parents will know where we went. They'll send people down here, figure out what's going on, and make sure someone comes after us." I wasn't actually sure that was true-once the government found out about this operation, three missing teens might be pretty low on their list of priorities-but it seemed to be the telling argument. Lips tight, he finally nodded.

Moving inert human bodies turned out to be a lot harder than you'd think, especially when you're trying not to bang them against tables or rock. As we positioned them behind a cl.u.s.ter of thick formations, Rita pointed out that our backpacks couldn't ride on the gurneys with us without being visible. We didn't want to leave them behind, so I jury-rigged a quick support line to hang mine underneath the tabletop, and the others followed suit. Thank G.o.d for duct tape. The sheets were just long enough to hide our packs from sight, a.s.suming the fabric stayed in place.

Then, one by one, we laid down on the sleek steel slabs, arranging ourselves like corpses. Rita covered Devon and me with our sheets, taking care to make sure they were arranged the same as the ones covering the other bodies. She had to arrange her own after that, and I prayed it would be convincing. The things these people might do to us if they discovered our little trick didn't bear thinking about.

No sooner were we settled in when we heard footsteps again. I tried to minimize my breathing as they approached, so that the rise and fall of my chest wouldn't give me away.

People walked around us. They talked. I concentrated on my heartbeat, my breathing, listing in my mind the thousand and one things we probably should have talked about before doing this . . . anything but what was happening in the world beyond my sheet. I couldn't afford to react to events in the room, even reflexively.

Then the strange pattern filled my brain again. Golden lines, dancing and weaving all about me. This time they felt familiar, as though I had seen them somewhere before. As though I should know what they meant.

Suddenly the steel table beneath me jerked into motion. I held my breath for a moment-and then reconsidered, and risked one deep, slow inhalation to fill my lungs. You never knew when you might need air.

The golden patterns surrounded me, caressed me, penetrated me. For a moment I was an integral part of them, and nothing else in the universe mattered.

Then suddenly everything was gone, save my fear and my sweat and the cold touch of steel beneath my fingertips. We had left our world behind.

Hang on Tommy! I'm coming for you.