Nine keys hung on the wall. The door had one lock. This is the sort of arithmetic that keeps a person up at night, and it had kept Ada up for three of them.

But tonight was the night. She was sleepless in her bed. She got up, and slammed her bedroom door open. She went down the stairs, picked the oldest looking key, and opened the lock. Click. The door opened. Creak. Darkness. A red glow. Ada stepped through the door, which snapped shut and vanished behind her. She was in a huge dark cave on the other side. It wasn’t a room. There was someone - something, in the distance, in the center of the cave.