A community parade turns deadly in a case that brings family tensions and politics to the forefront. Maura, who is dealing with her own family issues, is not quite herself. And a surprise visit from Lt. Col. Casey Jones (guest star Chris Vance) reveals some shocking news.
While investigating the homicide of an overzealous journalism student, Jane is not happy when a former colleague returns to BPD as the new lieutenant of the drug unit (guest star Amaury Nolasco). But the murder she’s investigating soon forces her to deal with him – and the event wrecked their relationship. Meanwhile, an alarming tip from Cailin (guest star Emilee Wallace) causes Maura to investigate Hope (guest star Sharon Lawrence).
TJ's christening turns grim when a body is discovered in the church. Jane almost abuses her power in order to protect Tommy when Lydia's fiancé, Stuart Stawbridge (guest star Jareb Dauplaise) threatens to take custody of TJ, and budget cuts cause tensions to run high around the department.
Maura becomes the key suspect in a homicide case when Maura’s date turns up dead – and Maura can’t remember their evening together. As the shocking evidence against Maura piles up, Jane struggles between protecting her best friend and doing her job.
On the first day of Paddy’s (guest star John Doman) murder trial, Maura gains insight into her father from Hope (guest star Sharon Lawrence). Korsak opens up about Cavanaugh’s tragic past. And in an unexpected twist, Maura must decide which side she’s on when she and Jane unravel a shocking secret about Paddy and Hope that affects them all.
When a beleaguered Jane spills hot coffee on a stranger at Boston Joe's, a viral video of Jane’s bad day potentially jeopardizes her career and reputation. Meanwhile, the squad rushes to solve a puzzling murder case involving a conspiracy theorist.
A popular high school teacher is killed in a hit and run that is clearly no accident. The squad works to solve the case, but Jane is preoccupied with Lt. Martinez’s (guest star Amaury Nolasco) apparent favoritism towards his own drug unit.
Frankie Jr. is brought in to help with a gruesome murder case involving a youth hockey league. Frustrated with Hope, Cailin asks to stay with Maura. But Maura quickly learns that living with a teenager requires skills she does not have.
When Jane and Maura are asked to present the case of serial killer Charles Hoyt at a symposium for law enforcement, Jane worries that her greatest challenge will be facing bad memories. However, as she and Maura begin a simulation of investigating Hoyt’s murders, they soon come across a horrifying discovery. In a matter of moments, the team finds themselves drawn into a lethal game of cat and mouse with a new and terrifying serial killer.
When a late-night amateur drag race turns deadly, the squad works quickly to solve what turns out to be a particularly dangerous case. As evidence unfolds, Jane suspects that the motive for murder may have been an attempt to conceal drug trafficking. However, when she turns to Lt. Martinez for help he seems to be thwarting her investigation.
A mock trial advisor dies tragically during a competition. Meanwhile, Angela’s increased interest in selling brownies has Jane concerned that she may be hiding financial issues. And Tommy hires a lawyer to settle his claim against the Storrow Center.
The squad rushes to solve a violent homicide case muddied by conflicting evidence. Maura is burdened with the major decision of whether to take in her recently paroled grandfather. Meanwhile, Jane and Casey are forced to decide between their careers and their romantic relationship.