“Hello, there,” I said. “That was a very pretty feather. Where did you find it?”

He grinned, motioned for me to follow, then tore off.

“Wait,” I called. “I didn’t mean—”

He disappeared down a side hall. I followed. Medea could wait.

When I rounded the corner, the boy was standing in front of a door, dancing from foot to foot with impatience. Before I could call to him, he grabbed at the door handle and pantomimed opening it. It didn’t budge, but he acted as if it had, scooting through the imaginary opening.

The door led into a short hall lined with shelves and cleaning supplies. At the end, a hatch in the floor had been boarded over. Again, the boy went through the motions of opening it.

“I don’t think you should—”

He darted through. I walked to the hatch door, lowered myself to all fours, then pushed my legs through. Stuff like this was tricky—mentally disorienting. Like walking on floors or sitting on furniture in the living world. Seems simple enough, until you consider that those floors and that furniture don’t exist in my dimension. So what keeps ghosts from dropping through? Voluntary delusion. If you believe the floor exists or the chair exists, you can treat it as a physical object, at least in the sense that you won’t fall through it. So when passing through this trapdoor, I grabbed the floor and lowered myself down, even though I couldn’t feel anything under my fingers.

As my feet went through the boarded-up door, I cast a light-ball spell. My stronger magic might be hit-and-miss in this world, but I could still count on the simple stuff. Beneath the trapdoor was a ladder, a rickety half-rotted thing that promised to collapse under the slightest weight. Luckily, I was weight-free these days. So I set my foot onto the first rung, and climbed down.

I landed in a tiny, dark room. Concrete walls sweated rivulets of water that stank of sewage. I cast my light around. Nothing to see. Just bare walls and a bare dirt floor. I turned. On the wall behind me was a wooden door crisscrossed with boards. As I stepped toward it, something jabbed the bottom of my foot and I jumped in surprise.

I moved my light down to see a small green globe, half-buried in the dirt. Bending over, I picked it up. A marble. Jade green, its glassy surface clouded with scratches. I turned it over in my hand and smiled. A ghost marble, like the ghost wheelchair Kristof had conjured in the psych hospital. I tucked the marble into my pocket, then walked through the door.

I came out in a long hall. Doors lined one side, thick wooden doors reinforced with steel bands, solid except for a slit about two-thirds of the way up, covered with a metal plate.