The Unraveling — E.J. Findorff

If Ex-Detective Remi Doucet doesn't kill the governor of Louisiana by Mardi Gras Day, his teenaged daughter will suffer the same fate as his murdered wife. Remi must keep his mission a secret from the police and the FBI until he can figure out who had torn his world apart.  Partnering with Detective Gracie Castillo, the pair follow the clues left by dead bodies, arsonists, and Latino gang leaders, but Remi realizes that not all evidence is what it seems.