People who seem to have nothing in common are being killed in the Southeast U.S. Grace's autopsy yields that all the victims has the same rare blood type. It then becomes clear all the victims were related. The team uncovers evidence that confirms all the victims were the children of a Charles Manson-like cult leader currently incarcerated in a Georgia psychiatric facility. Sam interviews the adoptive parent of one of the remaining children and quickly surmises their son is the killer. She theorizes that he is killing his siblings to 'cleanse' himself of his deadly lineage. Once he kills his last target, the young man practically surrenders to police. Sam wonders why the murderer gives up so easily, and soon realizes it's just a piece of the plan that leads back to the cult leader father. The team races to the psychiatric facility where the father is being held. The son has had himself transferred there so that he might kill his father and finally make his cleansing complete. B-Story- Sam confronts her father about his unethical experiments.