here's rob stafford. >> 911. >> it's the worst news you could ever possibly have to deliver to somebody. >> on a saturday morning in an upscale atlanta suburb, a young son saw something no child should ever see. >> oh, he's going to remember it forever. >> where is he at now? is he with you? >> yes. >> okay. all right. how old is he? >> 7. >> he's 7? >> uh-huh. >> and what he saw would soon open the eyes of investigators to something they had missed for years. >> the deep, dark secret had been exposed. >> this is a tale of two tragedies, of two young women who lived and died at different times and in different cities but left behind a mysterious trail of almost identical clues. could solving one case lead to the truth in the other? for one family, the story began on december 4th, 2004. >> typical saturday morning. and the phone rang. and i was immediately hysterical. and i asked where she was, was she okay. and he said, "no, heather, i'm sorry, she's gone." >> she was 33-year-old jennifer corbin, the wife of dr. barton corbin, a tall, handsome dentist who was 40. they had been married s