Billy and the mysterious man stood in the deserted subway, staring at the rusted tracks that led away into darkness. "What are-" Billy began, but the stranger held up a hand and he fell silent. They stood for several minutes, just staring at the shadows on the walls. Just as Billy opened his mouth, the stranger whistled. It was just four simple notes, rising in pitch like birdsong, then trailing away into nothingness. But to Billy, it was so much more. The only person who had ever whistled like that, that simple four-note melody, was Billy's father. He whipped around, staring wide-eyed at the man in the trench coat. "Dad?" he whispered, "Is that you?" The stranger turned to him, then looked at the subway celling. He knows. He seemed to be talking to someone, but Billy couldn't hear anyone. He knows who I am; the bond is broken. He tilted his head, as if listening. Very well. Addressing Billy, We must enter the train, then I will tell you everything. "What train? I don't see any…" he trailed away, staring dumbfounded at the enormous bullet-shaped vehicle that was resting on the track less than three feet from where he stood. "Oh," he said quietly,"that train,".