dennis murphy (voiceover): rosie essa died in a low impact car accident. >> rosie died in a low impacts later, the family was still awaiting the coroner's final report on the exact cause of her death. >> that is when this woman on her own decided to get involved. and it's that involvement that would later prove invaluable to the police. >> i didn't want to be the nosy neighbor -- in bewitched. the gladys kravitz of the neighborhood coming up with these wild convoluted ideas. christine dicillo was a nurse who once worked with both rosie and her doctor husband yaz. she hadn't seen much of either of them in the previous five years. by coincidence christine lived right next door to roll rosie's a friend eva. -- giving her a calcium capsule. >> it's odd to me that just prior to leaving for a movie in the middle of the afternoon, in a hurry that was so necessary that he give you the pill. as soon as i got off the phone with eva, i look to my husband and said i think he killed her. >> gut instinct. >> instantly. >> so, going simply on her gut instinct, that something wasn't right. an unknown