The mirror girl came to me on the first of August, when the summer was almost over, and told me the rule.
"There is something I did not tell you," she said. "Something important."
We were in the hallway, and the house was quiet, and Delia and Henry were asleep. The mirror was glowing a little, the way it did at night, like the glass was full of light.
"What is it?"
"The mirror only works once," she said. "For each child, it only opens once. If you go back through, you can never come back. You will be real again, and the copy will be a copy again, and the mirror will close for you forever."
"And if I stay?"
"Then the copy stays real, and you stay here, and the mirror closes anyway, and you will never be able to go back even if you want to."
"So either way, I have to choose," I said.
