Rizzoli gets a bravery medal after escaping from a hostage situation. A brave US military private is also felicitated but is killed by a car bomb after the ceremony. Rizzoli, resting for the last three months and yet unfit, investigates.

After her boyfriend Casey Jones is unable to get to Boston, Jane takes Maura to her dreaded high school reunion. She hates most of the people there but one former classmate that she liked, Steve Sanner, says he would like to discuss something with her. Before he can do so however, Steve is shot and killed while taking a walk on the football field. The killer used a steel wool-filled water bottle as a silencer. He worked for another high school classmate, Rory Graham, who says he wasn't having any trouble at the office or with co-workers. Based on his phone records, they suspect he may have been having an affair with another former classmate, Debbie Tibbet, but when she is found dead her husband tells the police she had recently become very secretive. A third dead classmate gives them the clue they need to identify the killer. Meanwhile Vince Korsak's ex-wife is back in town wanting money for a new enterprise. Vince would like to see his 16 year-old son Josh.

Jane and Maura investigate the murder of an army veteran, 29 year-old Bernard Avery, who was killed in an alleyway with a hatchet. He was homeless, one of many ex-servicemen now living on the streets of Boston, and suffered from PTSD. When Rizzoli and Korsak visit a psychology center where Avery had sought help, Jane is surprised to find her old friend Casey Jones working there. He's been back for several months but refuses to tell her anything more. The police soon have a second dead homeless vet and Jane's informant, Rondo, thinks he's found a witness. Meanwhile, Maura meets Dennis Rochmond and after saving his life, he sends her orchids. She also discovers her wild side.

Young female professionals dressed as dolls are turning up dead on the public transit system, and Jane and Maura must piece together the clues. Angela implements new ideas for the café. And Jane learns more about how Casey was injured.

Casey drops some big news to finally explain to Jane why he's keeping his distance. Barry's mother plays ringer in an interoffice softball game then announces she's getting married. The detectives investigate the murder of a an ex-football player who ran a bakery.

Hope is ready to talk to Maura about a kidney for Cailin. Jane pays an unannounced visit on Casey. A substandard building related to a murder investigation endangers Jane's friends.

In the season premiere, a community parade turns deadly and family tensions and politics arise. A surprise visit from Lt. Col. Casey Jones (CHRIS VANCE) reveals shocking news.

The hit-and-run murder of a high school science and driver's education teacher focuses on a group of friends who were also students of the victim.

Two puzzling murders share a surprising link that could be the key to finding the perpetrators. Meanwhile, Jane and Casey come to a crossroad and Maura assumes caretaker for Patrick Doyle, Sr. who is being released from prison.

The Boston Police department is haunted from the past when a man in clown-costume almost kidnaps a little boy. Is it the same person that has molested and kidnapped boys in the 1980s?