Dr. Hope Martin returns to ask Maura for a life-altering favor. Jane worries about the impending spinal surgery for Lt. Col. Casey Jones, and Tommy shows off baby T.J. But all gets shoved to the side when a building collapses, trapping loved ones inside.

When a former college football player is stabbed inside a carwash during a fundraiser for his alma mater, Jane, Maura and the team must piece together clues to track down the killer. Meanwhile, Frost's mother visits Boston with some unexpected news. And Lt. Col. Casey Jones bumps into Jane and is forced to reveal some startling news of his own.

The virtual world and the real world collide when a microbrewer is killed. Angela tries to move on from a failed romance by seeing someone new. And Jane and the team begin to mentor underprivileged teenagers, a move that ends in near disaster.

A famous young writer of memoirs is found dead in an apparent suicide, but Jane and Maura soon discover there's more to the story. Meanwhile, Frost becomes obsessed with an old case involving a young African American student as his final appeal is denied. And Jane discovers Angela is involved in a secret romance.

When a man having breakfast in the Division 1 Café dies from poisoning, Jane and the team must quickly find the source as Angela and the irascible Stanley both come under scrutiny. Meanwhile, Tommy wants proof that he's the biological father of Lydia's baby as she returns to take the baby back. And Detective Korsak is reunited with one of his ex-wives.

When a statue breaks open to reveal a dead woman inside, Jane and Maura must find the killer quickly as the body count begins to rise. Back at headquarters, a new homicide detective is named to the squad. Meanwhile, Dennis Rockmond returns to Boston after disappearing on Maura and tries to woo her back. Lydia goes into labor.

A boy band star returns to his roots for a show and winds up murdered. Jane and Frankie, who grew up with the victim, work hard to solve the case. Meanwhile, Jane and Maura must decide if it's time to tell Angela the truth about Lydia's pregnancy just as Angela prepares to throw her a baby shower.

A bride is killed right before she walks down the aisle, and Jane and Maura must figure out if the groom's ex-girlfriend is a suspect, or if there's a deeper connection to the bride's European roots. On the homefront, Jane has a new neighbor who captures the attention of Angela, Frankie and Frost.

The detectives must piece together partial clues to lead them to the murderer of a husband-and-wife team of psychiatrists. Jane finds herself closer to the investigation than she realizes. Also, when the Boston Police Department hosts a seminar for Medical Examiners, one of the attendees, offers to help Jane and Maura on their case. Meanwhile, the Rizzolis have their hands full when they discover there may be a link to a pregnant stranger they've met.

When a rich financier is found stuffed in a trashcan wearing a cloak and mask, Jane and Maura must figure out what happened. Meanwhile, Maura makes a deeper connection with her biological mother, Dr. Hope Martin (guest star Sharon Lawrence), and half-sister, who still doesn't know Maura is related to them.

Jane looks for a way for Maura to meet her biological mother, Dr. Hope Martin. Angela gets involved in a political campaign. And a nun from Jane and Frankie Jr.'s past returns. Matthew Del Negro and Jenny O'Hara also guest-star.

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.

When Maura meets a new guy named Dennis in a very unusual way, he opens up a different side of her. And Jane is filled with mixed emotions after someone from her past returns.

Tensions continue to mount between Jane and Maura, causing those close to them to be caught in the middle. But they must put aside their differences when they investigate the case of a college student who died in a tunnel. Meanwhile, Frankie Sr. returns with news that upsets Angela.

Jane and Maura's friendship suffers following the shooting of Maura's biological father, gangster Paddy Doyle. Jane also finds herself in the middle of an Internal Affairs investigation. And her relationship with Agent Dean is exposed.