Anthony Horowitz said this quote

Much later that night, I thought the door opened and a man came into the bedroom. He was leaning on a stick. He didn't say anything but he stood there, looking sadly at Andreas and me, and as a shaft of moonlight came slanting in through the window, I recognized Atticus Pünd. I was asleep, of course, and dreaming, but I remember wondering how he had managed to enter my world before the thought occurred to me that maybe it was I who had entered his.