Chapter 1

"Slow down, kid," I whispered, but my voice came out sharper than I meant. He was nine and fearless, which meant he was also nine and reckless. My cousin Diego just shrugged and followed, leaving me to bring up the rear with the laptop bag slung over my shoulder and the two iron tokens clinking in my jacket pocket.

We had studied the parish ledger from 1793 until the ink blurred. A stone chamber beneath the mission chapel, sealed "for the keeping of what the world must not forget." The drawing showed a lock shaped like a mission facade, and beneath it the name of a master iron-worker: Alamo Iron Works. That was our family name. Our great-great-grandfather, or maybe his father, had forged the lock. We had the key. Or keys, technically.

The first token was the one that mattered. The one with the notches cut into its right side like the teeth of a key. The second was just a Rotary Club luncheon souvenir from 1978, which we figured Ruben's father had kept as a memento. But the notched token—that was the real thing.

I caught up to Diego and Nico at the side door of the chapel. It was a heavy wooden slab banded with iron, and it was locked. Diego pulled a set of picks from his pocket and grinned. "Don't tell Mom."

"I won't have to if you scratch the paint."

He didn't scratch it. Three minutes later the lock clicked and the door swung inward with a smell of old dust and dry incense. The chapel was smaller than I remembered from the daytime tours. Moonlight filtered through a high arched window and painted a silver stripe across the floor. Nico's flashlight danced over the altar, the pews, the faded fresco of a saint I couldn't name.

"The ledger said the chamber is beneath the sacristy," I said, pointing to a door on the left. "Behind the vestment cabinet."

We moved carefully, trying not to echo. The sacristy was a narrow room with a stone floor and a wooden cabinet that smelled of mothballs. Diego and I each took an end and shuffled it aside. Beneath it was a square of darker stone, maybe two feet across, with a shallow recess carved into its center.

I knelt and pulled out the notched token. It fit perfectly into the recess, the curve of the mission facade matching the edge of the stone. I pressed it down. Nothing happened.

"Try turning it," Nico said.

I tried. It didn't budge. "Maybe it's not the only key."

Diego frowned. "We only have one."

"We have two." I pulled out the Rotary Club token. It was dull, pitted, and seemed like a piece of junk. But I remembered the ledger's drawing—the lock had two slots, one on the left and one on the right. The left slot was the mission facade. The right slot was a circle.

I positioned the Rotary token over the right side of the recess. There was no circle carved there, but the stone had a faint ring-shaped discoloration. I pressed the token against it. It stuck. I felt a click under my thumb.

"Try now," I said.

I turned the notched token. It moved a quarter turn, then stopped. I pushed harder. The stone beneath my hand gave a grinding sound, and the whole square sank an inch into the floor. Dust puffed up around it.

Nico grabbed my arm. "It's opening."

The stone slab was not lifting up but sliding down, revealing a dark hole and a set of iron rungs set into the wall. A draft of cool, dry air rose from below. It smelled of earth and something metallic, like old blood or old iron.

"That's not a treasure chamber," Diego whispered. "That's a tomb."

"The ledger said it was a keeping place," I said. "For what the world must not forget."

I went first. The rungs were cold and solid, and I counted twelve of them before my foot touched stone floor. I flicked on my flashlight. The chamber was small, maybe ten feet square, with walls of rough limestone. In the center was a pedestal made of the same stone, and on the pedestal sat a leather-bound book and a small metal box.

No gold. No jewels. Just a book and a box.

Diego landed beside me, then Nico dropped down with a thump. "It's like a library basement," Nico said, disappointed.

"It's better than treasure," I said, though I wasn't sure I believed it. I approached the pedestal. The book was old, the leather cracked and flaking. I opened it carefully. The pages were filled with handwriting in Spanish, the ink brown with age. The first line read: "El mundo no es lo que parece. La realidad es un velo, y detrás de él hay otro velo."

"The world is not what it seems," I translated aloud. "Reality is a veil, and behind it is another veil."

Diego picked up the metal box. It was about the size of a shoebox, made of iron, with a small lock shaped like a star. "This one needs a different key."

I looked at the notched token still in my hand. The anomalies in its shape—the deliberate notches, the curve that matched the mission facade—had led us here. But the token was just the beginning. The real key was the knowledge we had uncovered, and there was more to unlock.

Nico tugged my sleeve. "Marisol, look at this."

He pointed to the wall behind the pedestal. There, carved into the limestone, was a map. It showed rivers, mountains, and a string of missions stretching south toward the Rio Grande. At the bottom was a symbol I recognized: the same mission facade from the token, but with a circle around it. Beneath the symbol were the words: "La llave del Alamo no abre puertas. Abre verdades."

The key of the Alamo does not open doors. It opens truths.

I felt a chill that had nothing to do with the cold air. We had found the chamber, but we had not found the treasure. The treasure was the map, and the map was a trail that led somewhere else. Somewhere deeper.

Diego let out a low whistle. "This is bigger than we thought."

"This is exactly as big as we thought," I said. "We just didn't know what we were thinking."

Nico was already tracing the map with his finger. "It ends here," he said, tapping a spot near the bottom. "Somewhere south of Eagle Pass. What's there?"

"Nothing," I said. "Or everything."

I closed the book and tucked it into my bag. Diego wrapped the iron box in his jacket. We climbed back up the rungs, pulled the stone slab into place, and slid the cabinet back over it. The mission was still dark and quiet. The moon had moved, and the silver stripe on the chapel floor was gone.

As we slipped out the service gate, I felt the weight of the notched token in my pocket. It was a key, but not to a door. To a truth. And the truth was that reality was a veil, and behind it was another veil, and behind that, something we were only beginning to see.

Nico stopped at the car and turned to face the mission. "We're going to find it, right?"

"We're going to try," I said.

"No," he said, with the certainty of a nine-year-old who has never been told no. "We're going to find it."

I looked at Diego. He was already pulling up maps on his phone. The hook was set. The adventure was just beginning, and I had a feeling that what we would find would change everything we thought we knew about the world—and about ourselves.