Kate Hamilton and her husband, Detective Inspector Tom Mallory, have settled into married life in Long Barston. When archaeologists excavating the ruins of a nearby plague village discover the miraculously preserved body of a fourteenth-century woman, Kate and her colleague, Ivor Tweedy, are asked to appraise the grave goods, including a valuable pearl. When tests reveal the woman was pregnant and murdered, the owner of the estate on which the body was found, an amateur historian, asks Kate to identify her and, if possible, her killer. Surprised, Kate agrees to try. Meanwhile, tensions within the archaeological team erupt when the body of the lead archaeologist turns up at the dig site with fake pearls in his mouth and stomach. Then a third body is found in the excavations. Meanwhile, Kate's husband Tom is tracking the movements of a killer of his own. With the help of 700-year-old documents and the unpublished research of a deceased historian, Kate must piece together the past before the grave count reaches four.