Following a harrowing mail bomb explosion, Detectives Harriet Shepard and Jasmine Alicia are thrust into an even more dangerous case. Former mentor T.J. Ramos returns from retirement as Tucson faces a new wave of bombings reminiscent of a past case they solved together. With the FBI’s interference and internal tensions, including Alicia’s career ambitions, Harriet must keep her composure and dismantle the bomber’s plot before another deadly explosion occurs.