Grandfather Piper amused his twin grandsons, Robin and Ricky, with tales of the greenjacks. They were harmless, he told them, unless you ventured out on Hallowe'en. Ricky could see them dancing in the garden; he could hear them calling out to him, and he could sense just how dangerous they really were. Robin could not see them, he was not afraid and he failed to heed their grandfather's warnings. He went into the garden on Hallowe'en. Then he returned to the house and there was something horribly wrong with him. Now Ricky has children of his own and he has to summon the strength to face up to the terrible secrets of his past. Then face an evil beyond imagining...