The Man from Beijing by Henning Mankell

REVENGE CAN TAKE MORE THAN A LIFETIME
In a sleepy hamlet in north Sweden, the local police make a chilling discovery; nineteen people have been brutally slaughtered. It is a crime unprecedented in Sweden's history and the police are under incredible pressure to solve the killings.
When Judge Birgitta Roslin reads about the massacre, she realises that she has a family connection to one of the couples involved and decides to investigate. When the police make a hasty arrest it is left to her to investigate the source of a nineteenth century diary and red silk ribbon found near the crime scene. What she will uncover leads her into an international web of corruption and a story of vengeance that stretches back over a hundred years.
The Man from Beijing is a gripping political thriller and a compelling detective story from a writer at the height of his powers.