A body discovered in a park appears to be the work of Charles Hoyt, the imprisoned serial killer who once abducted and nearly murdered Jane. As Maura tries to get inside the mind of the killer, Jane struggles with keeping her fear in check.

After an undercover cop working a narcotics-smuggling sting is shot dead, the killers next turn their sites on Boston homicide headquarters, leaving Jane, Maura and Frankie Jr. trapped in a fight for survival on their home turf. It's a situation that will force Maura to challenge herself like never before.