Dr Sarah Baldwin races to a Boston hospital with a young woman whose normal labour has suddenly become a matter of life and death. As she struggles to save both mother and baby, she doesn't know that two other women have already died under horrifying identical circumstances. And so begins Sarah's own nightmare, as she learns that the prenatal herbal vitamins she prescribed are the only things these three women have in common. Soon Sarah is fighting to save her career, her reputation - her life. For she's certain there must be some unknown factor linking these women, and as she gets closer to the truth, it becomes clear that someone will do anything - even murder - to keep a devastating secret.