The Widows by Pascal Engman (used)

Two bodies are discovered in a Stockholm park, one a policeman and the other an unidentified young woman, With the police believing the woman to be nothing more than unfortunate collateral damage, they focus on the murder of the police officer. But Detective Vanessa Frank takes a different approach and her investigation turns out to be more personal than she could have imagined. 

 Frank must tread carefully as she moves into the world of terrorists networks operating deep within the shadows, where society's make her job more chaotic and dangerous than ever. When those being hunted are bound together by grief and driven to revenge ,the consequences are devastating.