"I don't know," I replied. "But I'm pretty sure this wasn't here last time. Come on, let's keep going."
As we went, the walls began to change colour. Some of them became lighter and more transparent, while others darkened and grew thicker. But the strangest thing about them was the amount of light that shone through them. At first the light was faint, but it soon grew stronger and brighter as we continued.
Soon we found ourselves walking through a tunnel where the walls were made entirely of mirrors. On the floor was an empty pool of water, which was exactly the same colour as the wall behind it.
"Wait!" Leah suddenly called out. She had stopped dead, and now she was staring at the wall in front of us. Her eyes were wide open, as though she had only just realised something important. Th
