"It happened one hot July night, the air-conditioner groaning, the computer screen pulsing with a manuscript that was due NOW. My mind wandered away from my work. I thought about a strange abandoned subway station I'd seen that day. As our train had raced past dimly lit graffiti-covered walls and soot-carpeted floors, I imagined the ghosts of waiting passengers -- and I wondered what would happen if the train had stopped there, the doors had opened, and someone had walked out. And what if only one person could see it? And what if that were part of some master plan, watched over by unseen guardians?