We hadn’t yet turned on our flashlights, so I’m not entirely sure why we had them. But when footsteps suddenly echoed through the hall, I was glad we hadn’t turned them on. Veronica held out a hand, and we all stopped behind her. She turned, excitement in her eyes, and motioned us back with a hand. We tiptoed back a few steps, then crowded into one of the semicircular alcoves in the hallway. I gnawed my lip as I tried to control my breathing, sure that the thundering beat of my heart was echoing through the hallway for all to hear.

After what felt like an hour, the sound of footfalls faded as the person—probably one of the clipboard-bearing dragon ladies—moved off in the other direction.

Veronica peeked out of the nook, one hand behind her to hold us back while she surveyed the path.

“Okay,” she finally whispered, and we set off again—Veronica, then Mary Katherine, Amie, and I. I couldn’t help but glance behind us as we moved, but the hall was empty except for the cavernous silence we left in our wake, and the moonlight-dappled limestone floor.

We continued down the administrative hallway, but before we got as far as Foley’s office, we turned down a side corridor that dead-ended in a set of limestone stairs. The air got colder as we descended to the basement, which didn’t help the feeling that we were heading toward something unpleasant. We probably were headed toward the nasty that had been chasing Scout, but I couldn’t imagine the brat pack had any clue what lurked in the corridors beneath their fancy school. If they had known, they surely would have tortured Scout about it. They seemed like the type.

“Almost there,” Veronica whispered as we reached the bottom of the staircase. True to St. Sophia’s form, we entered another limestone hallway. I’d heard about buildings that contained secret catacombs, but I wondered why the nuns had bothered building out the labyrinthine basement of the convent—a task they’d taken on without trucks, cranes, or forklifts.

“Here we are,” Veronica finally said as we stopped before a simple, wooden door. The word CUSTODIAN was written in gold capitals across it, just like the letters on Foley’s office.

I arched an eyebrow at the door. “We’re going into the janitorial closet?”

Without bothering to answer, Mary Katherine and Veronica fiddled with the brass doorknob, then opened the door with a click.

“Check it,” Veronica said, grinning as she held the door open.

I walked inside, and my jaw dropped at the scene before me.

The room was a giant limestone vault, completely empty but for one thing—it held an entire, little Chicago, a scale model of the city. From a two-foot-high Sears Tower and its two gleaming points (which even I could recognize), to the Chicago River, to the Ferris wheel at Navy Pier. All in miniature, all exactingly detailed, laid out across the floor of the giant room by someone who clearly loved Chicago—someone who knew Chicago.

“Who did this?” I asked.

“No clue,” Veronica said. “It’s been here as long as we’ve been here. Pretty sweet, huh?”

“Very,” I muttered, eyes wide as I walked the empty perimeter of the limestone room, just taking it all in.

The model was almost totally devoid of color—the buildings and landscape rendered in various shades of thin, gray cardboard—but for symbols that were stamped on a few points across the city. In navy blue was a symbol that looked like four circles stuck together, or a really curvy plus sign. In apple green was a circle enclosing a capital Y.

Markers, I thought, pointing out the locations of two kinds of something across the city.

I moved into the middle of Lake Michigan—an empty space across the floor—and peered between the buildings, looking for St. Sophia’s. When I found East Erie, I realized there were two symbols nearby: the four-circle thing on Michigan Avenue and, more interesting, the enclosed Y only a couple of blocks from St. Sophia’s. “What do the symbols mean?” I asked.

I got only silence in response.

I glanced up and looked behind me just in time to watch them shut the door, and just in time to hear the lock tumblers click into place. I hurdled Navy Pier, ran to the door, gripped the doorknob in both hands, and pulled.

Nothing.

I shook it, tried to turn it, pulled again.

Still nothing, not even a knob to unlock the door from the inside. Just a brass keyhole.

“Hello?” I yelled, then beat my fist against the door. “Veronica? Amie? Mary Katherine? I’m still in here!”

I added that last part in the off chance they were somehow unaware that they’d locked me into a room in the basement of the school; in case they’d forgotten that the four of us had traveled the halls of St. Sophia’s to get to this underground room, but only three were headed back up.

But it wasn’t an accident, of course, and the only answer I got back was giggling, which I could hear echoing down the hallway.

“Way mature!” I yelled out, then muttered a curse, mostly at my own stupidity.

Of course there was no candy, no Tab, no hidden cigarettes, or black-market energy drinks down here. There was a treasure—the brat pack had stumbled upon something, a hidden room that contained an intricate scale model of the city. But they’d probably missed the point, being only interested in how to use the room to prank me—how to punk me.

I kicked a foot against the door, which did nothing but vibrate pain up through my foot. Turned out, even my favorite boots didn’t provide much more insulation than flip- flops. I braced one arm against the door and rubbed my foot with my free hand, berating myself for following them into the room.