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.

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 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.

A kidnapper dressed as a clown re-emerges after 20 years; Jane's relationship with Casey grows more serious; Maura inadvertently gets in the middle of another relationship.