While Hayes and Wallace struggle to balance their professional and personal lives, they are summoned to a crime scene that fits the M.O. of the infamous “Black Orchid Killer.” Is the latest murder the work of a copycat? Or is the man now in prison for the earlier crimes actually innocent? As the investigation accelerates, the CIU team, spearheaded by unlikely serial-killer expert Tess, closes in on a suspect who may have committed all the murders – but will it be too late?