The realtor called the staircase a "feature." It dropped past our new cellar, past a wine room nobody asked for, all the way down to a cold concrete floor. In Hollow Marsh, every house had one, each deeper than the last, like the town was competing. Our first night, Mrs. Edevane from next door knocked. "Whatever you do," she said, "don't go past the frost line."

I asked Mrs. Edevane what the frost line was. She pointed at my feet. "You'll feel it. The step where the air turns to ice. Below that, the house stops being yours." Then she left a thermos of soup and hurried home. I stood at the top of the stairs, looking down into the dark.

I went down to find the frost line myself. Twenty steps, then thirty. The wine room glided past. Around step forty the air bit my lungs and my breath came out white. One more step and the cold turned solid, like walking into a wall of winter. This was it.

I touched the frost line with one finger and the cold ran up my arm like a shock. Below me, in the dark, dozens of voices sighed at once, happy I'd finally reached them. A hand made of frost closed gently around my ankle and pulled. I grabbed the rail and screamed for Dad.