When is cold-blooded murder justified?

When is cold-blooded murder justified?

New Orleans Detective Nikki Mayeaux has decided it's when a technicality sets a serial rapist free.

Jaded and frustrated, this latest injustice brings her to a boiling point. She arrives at the monster's home intending to end his reign of terror, only to find someone else got there first. His throat slit, his lifeless body left in the front seat of his car.

Only one person wanted him dead more than her - his final victim - a girl of only sixteen who has vanished in the seedy underbelly of the French Quarter where residents will go to great lengths to protect their own, even when their own is a killer.

When is cold-blooded murder justified?