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."

My little brother Theo didn't wait for warnings. By the time I turned around, he was already three steps down, giggling, counting each one out loud. "Seven, eight, nine," he sang. His voice echoed up wrong, like the stairs were much longer than they looked.

I chased Theo down, grabbing his hood just past step twenty. He pointed deeper into the dark. "There's people down there," he whispered. "They waved at me." I looked. Far below the frost line, pale shapes stood in a row, perfectly still, all of them facing up at us.

I waved back at the pale shapes, just to be polite. Big mistake. The whole row waved at once, then began climbing, fast and smooth, never blinking. I shoved Theo up the stairs ahead of me. We made it out and bolted the door, panting. From the other side came a soft, patient knock. They could wait. They had time.