Detective Jane Rizzoli and medical examiner Maura Isles investigate the grisly murder of a wealthy couple. The M.O. matches the work of a serial killer known as the Surgeon, who once nearly murdered Jane. Now that the Surgeon is behind bars, it seems one of his proteges is picking up where he left off.

Tensions are high as the squad investigates a possible copycat of the legendary Boston Strangler…or could it be the Boston Strangler himself? Meanwhile, Jane butts heads with her new boss, Lt. Grant, who just happens to be from the same neighborhood where Jane grew up. And Maura gets into trouble with her habit of diagnosing everyone – including her date.

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. On the home front, Jane's parents are excited that their oldest child, Tommy, is being released after serving time in prison.