Struggling Boston attorney Scott Finn is happy to do any legal work-until he lands the most twisted case of his career. Fifteen years ago, a female cop was viciously beaten and shot. Fingerprint evidence sent a man named Vincente Salazar to prison for fifty years. But today new DNA clues suggest he's innocent-and Finn is determined to find the truth. Then the cops block his investigation and the victim, who survived, won't talk to him. As his case unravels, Finn is shocked to discover that many of Boston's finest are risking their badges-and even their lives-to lie about this crime. Now the thin blue line between guilt and innocence stretches from Central America to the Boston suburbs . . . and is about to entangle Finn in its deadly web.