Special Agent Maggie Bell, Special Agent OA Zidan and the team investigate the murders of 18 young women with help from a survivor associated with the deceased.

When an illegal arms broker turned informant is assassinated, OA assumes his identity and goes undercover to stop the sale of dangerous weapons, with help from Maggie and their former FBI instructor, Rowan Quinn.

Maggie and Dana struggle to find justice for victims murdered by a serial killer who left a ghoulish mark on all of his victims, while the mayor limits the investigation in order to prevent economical loss.