Pushing the air vent open, I pulled out a bundle. “Here, put this on.” I handed Logan the coveralls Riley had given me. While he dressed, I donned the student’s uniform. The black jumper with silver piping along the pants and sleeves sagged around my waist, but I cinched it tight with the belt.

When he was ready, I climbed into the air shaft and helped Logan inside.

“It’s bigger than the heating vent,” he said.

“Sounds still carry, and I’m about to show you a place only I know about. You can’t tell anyone. Not even Anne-Jade. Promise me?”

“Ooh. Sounds like fun. Of course, I promise.”

I slid through the shaft, stopped under the near-invisible hatch and pushed it open. Logan pressed a hand to his mouth to smother his cry of surprise. Turning on my light, I climbed into the meter-and-a-half-high space and moved aside so Logan could join me. He stared at his surroundings while I closed the hatch.

“What is this place?” he asked in a whisper.

I shrugged. “I call it the Gap. There’s one between each level.”

“Wow. What’s it used for?”

I gestured around. “Space for the pipes and wires. I think everyone’s forgotten about it. I can only get in here through one near invisible hatch on each level. Come on, but crawl quietly.” I hurried toward the lift. The easiest way to get Logan up to the fourth level was by riding on top of the lift.

A meter-high metal barrier divided the Gap from where the lift cut through the four floors of Inside. From the inside of the lift, it appeared the shaft was solid, but each level had a half-meter opening into the Gap. I pulled my extendable mirror from my tool belt. Shining the light in the shaft, I used the mirror. The lift was on the third level.

“When the lift comes down to our level, we don’t have much time but we need to quietly move onto the roof and stay there until we reach the top,” I said.

“What happens at the top?” Logan bit his thumbnail.

“We climb into the Gap before the lift descends.”

Logan stared, and nibbled on his nails. If he were a computer, he would be making the rumbling crunching noise that meant it was calculating.

“Once we’re on, do we have to wait until an upper wants to go to level four?” he asked.

“No. Once it’s down, there are override controls on the roof.”

Logan shivered as we waited. “It’s cold here. I wonder why there is all this extra room. Does the Gap run the entire length of Inside?”

I explained how each level was connected by steel I-beams to the Wall.

“How about under the lower level, is there a Gap there?” he asked.

“Yes. All the levels are surrounded by Gaps.”

“What’s beyond the Gaps on the sides?”

“The Walls of Inside.”

He considered. “What do the Walls feel like?”

“There’re covered with insulating foam.”