Where the Devil Won't Go — E.J. Findorff

On the heels of having shot an innocent girl while in the grasp of a killer, Detective Peyroux's first case back is a young Jane Doe washed up on the banks of the Mississippi River. After learning her identity, Detective Peyroux travels to the bayou to notify the family. When the dead woman's teenaged sister disappears and bad people start turning up dead, Detective Peyroux realizes he has a vigilante on his hands. Can Peyroux find her before she kills an innocent or possibly ends ups dead herself?