Season 4 premiered on June 25, 2013 and ended on March 18, 2014, consisted of 16 episodes. Season 4 was in a hiatus due to Lee Thompson Young's sudden death. This was another reason for the larger-than-normal Mid-Season break.
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 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. 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 causes Maura to investigate Hope.
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 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 murder trial, Maura gains insight into her father from Hope. 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 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.
The squad tries to solve a homicide case that is muddied by conflicting evidence; Maura must decide if she is going to take in her recently paroled grandfather; Jane and Casey must decide between their careers and their relationship.