Kansas City is the home of an annual ritual now known as "Blood Week." For the past four years, a vigilante has killed seven criminals over seven days and displayed their mutilated bodies as artwork for the masses. As the fifth anniversary approaches, the public debates whether murder can be justified.

Detective Alexander Saint is a playboy with a trust fund, but he takes his job seriously. He and his recently transferred partner, Marcus Delgado, have been assigned to find the Blood Week killer. The only evidence is the word reus Latin for "accused" that has been carved into the bodies of each victim.

The detectives search for the killer in an investigation that forces them to deal with the morality of the killer's actions. The vigilante is doing them a favor by cleaning up the streets, but, in the process, he has declared himself judge, jury, and executioner. Saint and his partner must decide where they stand and where they draw the line between justice and murder.