When the first hate letter arrives in the days after her patient, Bonnie's death, obstetrician Doctor Dana Cavanagh reads it with shaking hands before placing it next to the small news article of the court's verdict: not guilty. Hate letters continue to trickle in, but one stands out from the others-a cryptic message with a tiny marble stone, its origin-Kos, Greece, the birthplace of Hippocrates. She had once proudly sworn his oath, "I will give not deadly medicine." Accompanied by her sister Madeleine, Dana follows the mystery of the letter to Kos. The arrival of two more letters, and the strange appearances of a woman, beckon her to Italy and England. Despairing for her sanity, Dana persists in her crusade to come to terms with being implicated in the death of another.