Vengeance Is Mine — M.R. Miller

Emily O'Brien is slowly putting the pieces of her life back together after her husband, a state trooper, is killed during a traffic stop. But six months after his death, she finds an envelope behind his desk that sends her searching for answers about a case he was secretly working when he died. Soon she's convinced his death was no random act of violence; it may have been necessary to quiet his investigation into the deaths of six drug runners.
Drawing on her years working the crime beat for a major Chicago newspaper, Emily begins asking questions about Alex's death. Her inquiries take her from a tornado-ravaged community searching for a way to recover to a wealthy and powerful family with political aspirations and connections. As the dots begin to connect, it becomes evident that the same people who killed Alex are beginning to target her as well, forcing Emily to seek protection from some very unlikely sources.
As she draws closer to the truth, Emily must face the rage driving her toward vengeance, a rage that is just as dangerous to her soul as the threats against her life.