When Brigida Uto arrives at an emergency room, she is near death. While her vital signs are fading, there are no signs of an infection or injury. Doctors, the FBI and local law enforcement are all called in to not only try to solve a medical mystery, but also a horrendous crime..Natalie Morales has chosen this episode as one of her most memorable episodes.Tune in to Dateline’s 30th season premiere Friday at 9/8c on NBC.