After an attack on the night of her 21st birthday, Aspen Rigby awakens within the walls of Division 27 - a clandestine organization part of a circle of central intelligence that is kept a secret from the outside world. While trying to adjust to her new life and fight off the demons of her past, she's also faced with the shocking realization that, with a target on her back, she needs to be careful where she puts her trust, as well as how she decides to fight at a crossroads.

While investigating the chilling deaths of three teenage girls in the remote town of Briarwood, Detective Evan O'Riley is drawn into the unsolved mysteries of a notorious 1960s serial killer. Three sixteen-year-old girls have plunged from the roof of their school. The question lingers: did they jump, or were they pushed? Tasked with uncovering the truth, Evan O'Riley-seasoned by years of crime-solving in Riverton-arrives in Briarwood, determined to discover whether he's facing triple homicide or a heartbreaking suicide. As he delves into the case, Evan uncovers unsettling whispers about the town's infamous SAD Killer, whose string of brutal murders left Briarwood haunted-and whose identity was never discovered. Fifty years later, the ghosts of the past resurface as Evan combs through long-buried evidence, tracks down survivors, and seeks out old investigators tied to the original crimes. Driven to find answers for both the present and the past, Evan is relentless in his pursuit of justice. But as old secrets come to light and the investigation intensifies, Evan realizes the SAD Killer's legacy isn't as distant as he believed-the danger may be closer than anyone imagines.