You leave us alone; we'll leave you alone. When Elaine Mercado and her first husband bought their home in Brooklyn, N. Y., in 1982, they had no idea that they and their two young daughters were embarking on a thirteen-year nightmare. Within a few days of moving in, Elaine and her older daughter began to experience the sensation of being watched. Then came scratching noises and weird smells, followed by voices whispering, maniacal...