When Special Agent Will Trent arrives in Grant County, he finds a police department determined to protect its own and far too many unanswered questions about a prisoner's death. While the police force investigates the murder of a young woman pulled from a frigid lake, Trent investigates the police force. Caught between two complicated and determined women, and the complexities of this insular town, Trent will unleash a case filled with explosive secrets, and encounter a thin blue line that could be murderous if crossed.