On the day of the General Election in 1992, a man is stabbed to death in a country church. The murderer is caught quickly, confesses and is convicted. He dies in prison shortly afterwards, having never disclosed the reasons behind his actions. Twenty-three years later, a recently retired crime reporter decides to write a book about the murder, hoping to uncover the motive. He establishes that the murdered man was a genealogist researching parish records held in the church, and he suspects that therein lies the answer. Being unfamiliar with the ins and outs of family history research, he calls on the expertise of local genealogists Madeleine Porter and her husband Ian Clay. However, their investigations are soon thrown off track when Ian receives a surprising letter.