When Hauser, Madsen, and Soto track former inmate Paxton Petty, a landmine bomber who has returned and is placing bombs throughout populated areas of San Francisco, methods of the past are applied to the present.

Madsen and Hauser hunt down Johnny McKee, a former Alcatraz inmate and vicious killer with a background in chemistry. It’s a race against time before McKee horrifically poisons more innocent victims. Meanwhile, more details emerge about Madsen’s grandfather.

Sonny Burnett, a man with a dark side, who became extremely violent while at Alcatraz reappears.

Clarence Montgomery was the only innocent man in Alcatraz, but he's returned and is committing crimes.

Rebecca, Doc, and Hauser set out to capture musically-inclined serial killer Webb Porter, an unknown ’63 that returns more violent than ever.