January 2006. In the Swedish hamlet of Hesjövallen, nineteen people have been massacred. The only clue is a red ribbon found at the scene. Judge Birgitta Roslin has particular reason to be shocked - Her grandparents, the Andréns, are among the victims, and Birgitta soon learns that an Andrén family in Nevada has also been murdered. She then discovers the nineteenth-century diary of an Andrén ancestor - a gang master on the American transcontinental railway - that describes brutal treatment of Chinese slave workers. The police insist that only a lunatic could have committed the Hesjövallen murders, but Birgitta is determined to uncover what she now suspects is a more complicated truth.