Doc and Rebecca close in on a man who may be the key to revealing the secrets behind all the returning criminals. Meanwhile, Hauser makes a discovery beneath the halls of Alcatraz that brings him ever closer to the truth.
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.
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.
Guy Hastings, an Alcatraz guard, reappears. Although a good man, Hastings is being asked to do bad things and will come face-to-face with an old acquaintance.
When a bank robbing criminal returns from the past and things go wrong in the present, Rebecca has to break him out of the hostage-filled bank before people can find out who he is.
When child killer Kit Nelson, a terrifying kidnapper who always returns his victims home - after he's killed them - reappears from the past, the team is in a race against time to catch the man before he kills again.
Years ago when the most dangerous prisoners of Alcatraz mysteriously disappeared, they resurface in the present day as part of a larger conspiracy, leaving a police detective, an expert on Alcatraz and an FBI agent to track them down.