It was supposed to be the house of their dreams. Now their million-dollar house is worthless. They were forced out when an invisible poison moved in. The whole family got sick - including their young son. 48 Hours tells their story, and shows how bacteria and viruses can infiltrate our lives. Correspondent Erin Moriarty reports on a family whose dream house was transformed into a nightmare by a poisonous mold. The mold spread throughout the house and forced them to leave. Did it cause brain damage? It was a simple visit to the county fair that ended tragically. Peter Van Sant reports on how a small drink of contaminated water scarred a family forever. Last year, Cody Unser, an energetic, athletic 12-year-old, was paralyzed by a puzzling virus. Troy Roberts reports on how Cody, the daughter of auto racing legend Al Unser Jr., is coping with her condition. Peter Van Sant takes a "germ tour" of Tucson, Ariz., with microbiologist Charles Gerba. How contaminated are most everyday places? Find out. Bill Lagattuta reports on Strep B, a bug that can kill newborn infants. See what happened to two families whose children had the disease.